# What is Galvanizing



## سيد صلاح الصاوى (1 يوليو 2014)

see attached link

https://www.youtube.com/watch?v=f6WYxkhum-s

This video gives you a close up look at the hot dip galvanizing process while explaining the benefits of protecting metal


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## سيد صلاح الصاوى (2 يوليو 2014)

Galvanizing procedure
see attached file


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## سيد صلاح الصاوى (2 يوليو 2014)

Petroget Galvanizing procedure 
see attached file


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## سيد صلاح الصاوى (2 يوليو 2014)

EN Is 1461 Hot dip galvanized coting
see attached file


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## سيد صلاح الصاوى (2 يوليو 2014)

*Galvanization*

From Wikipedia, the free encyclopedia

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"Galvanize" redirects here. For other uses, see Galvanize (disambiguation).
Not to be confused with galvanism.

 
This article *needs additional citations for verification*. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. _(May 2012)_

 
A street lamp in Singapore showing the characteristic spangle of hot-dip galvanization.


*Galvanization* is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani. Although galvanization can be done with electrochemical and electrodeposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc. In industry, the term _GI_ stands for _galvanized iron_, referring to a common galvanized steel used in many applications such as air ducts and trash cans.
*Contents*




1 Meanings
1.1 Metal protection
1.2 History

2 Zinc coatings
2.1 Eventual corrosion
2.2 Galvanized piping

3 See also
4 References
5 External links


*Meanings[edit]*

*Metal protection[edit]*

In current use, the term refers to the coating of steel or iron with zinc. This is done to prevent rusting of the ferrous item. The main purpose of galvanizing is to protect the underlying metal from corroding. Galvanzizing accomplishes this two ways: First, it forms a barrier coating. Under most service conditions, zinc resists corrosion much better than iron or steel, and prevents corrosive substances, such as water, from reaching the more delicate metal. Second, the zinc serves as a sacrificial anode, so that it cathodically protects exposed steel. This means that even if the coating is scratched or abraded, the exposed steel will still be protected from corrosion by the remaining zinc. The coating aspect is similar to paint, enamel, powder coating and other methods, but the sacrificial aspect is unique to metal coatings.
The term galvanizing, while technically referring specifically to the application of zinc coating by the use of a galvanic cell (also known as electroplating), is also generally understood to include hot-dip zinc coating. The practical difference is that hot-dip galvanization produces a thick, durable and matte gray coating - electroplated coatings tend to be thin and brightly reflective. Due to its thinness, the zinc of electroplated coatings is quickly depleted, making them unsuitable for outdoor applications (except in very dry climates). When combined with subsequent painting (which slows zinc consumption), electroplating is durable enough to be used in some premium auto body coatings.
Nonetheless, electroplating is used on its own for many outdoor applications because it is cheaper than hot dip zinc coating and looks good when new. Another reason not to use hot dip zinc coating is that for bolts and nuts size M10 (US 3/8") or smaller, the thick hot-dipped coating fills in too much of the threads, which reduces strength (because the dimension of the steel prior to coating must be reduced for the fasteners to fit together). This means that for cars, bicycles and many other 'light' mechanical products, the alternative to electroplating bolts and nuts is not hot dip zinc coating but making the bolts and nuts from stainless steel (known by the corrosion grades A4 and A2).
*History[edit]*

Originally, "galvanization" was the administration of electric shocks (in the 19th century also termed _Faradism_, after Michael Faraday). It stemmed from Galvani's induction of twitches in severed frogs' legs, by his accidental generation of electricity. Its claims to health benefits have largely been disproved, except for some limited uses in psychiatry in the form of electroconvulsive therapy (ECT). This archaic sense is the origin of the meaning of _galvanic_ when meaning "affected/affecting, as if by a shock of electricity; startled".[SUP][1][/SUP] and the metaphorical "galvanize into action" referring to suddenly stimulating a complacent person or group to take action. Later the word was used for processes of electrodeposition, which remains a useful and broadly applied technology. But the term "galvanization" has largely come to be associated with zinc coatings, to the exclusion of other metals.
Galvanic paint, a precursor to hot-dip galvanization, was patented by Stanislas Sorel, of Paris, France in December, 1837.[SUP][2][/SUP]
The earliest known example of galvanizing of iron was found on 17th century Indian armor in the Royal Armouries Museum collection.[SUP][3][/SUP]
*Zinc coatings[edit]*

Main articles: Hot-dip galvanizing and Sherardizing
Zinc coatings prevent corrosion of the protected metal by forming a physical barrier, and by acting as a sacrificial anode even if this barrier is damaged. When exposed to the atmosphere, zinc reacts with oxygen to form zinc oxide, which further reacts with water molecules in the air to form zinc hydroxide. In turn, zinc hydroxide reacts with carbon dioxide in the atmosphere to yield a thin, impermeable, tenacious and quite insoluble dull gray layer of zinc carbonate which adheres extremely well to the underlying zinc, so protecting it from further corrosion. This is similar to the protection afforded to aluminium and stainless steels by their oxide layers.
*Hot-dip galvanizing* deposits a thick robust layer that may be more than is necessary for the protection of the underlying metal in some applications. This is the case in automobile bodies, where additional rust proofing paint will be applied. Here, a thinner form of galvanizing is applied by electroplating, called "electrogalvanization". The hot-dip process does generally not reduce strength on a measurable scale,[SUP][4][/SUP] with the exception of high-strength steels (>1100 MPa) where hydrogen embrittlement can become a problem.[SUP][5][/SUP][SUP][6][/SUP] This is a consideration for the manufacture of wire rope and other highly stressed products. The protection provided by hot dip galvanizing is insufficient for products that will be constantly exposed to corrosive materials such as salt water. For these applications, more expensive stainless steel is preferred. Some nails made today are electro-galvanized.
As noted previously, both mechanisms are often at work in practical applications. For example, the traditional measure of a coating's effectiveness is resistance to a salt spray. Thin coatings cannot remain intact indefinitely when subject to surface abrasion, and the galvanic protection offered by zinc can be sharply contrasted to more noble metals. As an example, a scratched or incomplete coating of chromium actually exacerbates corrosion of the underlying steel, since it is less electrochemically active than the substrate.

Galvanized surface with visible spangle


The size of crystallites in galvanized coatings is a visible and aesthetic feature, known as *spangle*. By varying the number of particles added for heterogeneous nucleation and the rate of cooling in a hot-dip process, the spangle can be adjusted from an apparently uniform surface (crystallites too small to see with the naked eye) to grains several centimetres wide. Visible crystallites are rare in other engineering materials.
*Thermal diffusion galvanizing*, a form of Sherardizing, provides a zinc coating on iron or copper based materials partially similar to hot dip galvanizing, but the final surface that results is different from that yielded with hot-dip galvanizing in that all of the zinc is alloyed.[SUP][7][/SUP] Zinc is applied in a powder form with "accelerator chemicals" (generally sand,[SUP][8][/SUP] but other chemicals are patented). The parts and the zinc powder are tumbled in a sealed drum while it is heated to slightly below zinc's melting temperature. The drum must be heated evenly, or complications will arise. Due to the chemicals added to the zinc powder, the zinc/iron makes an alloy at a lower temperature than hot dip galvanizing. This process requires generally fewer preparatory cleanings than other methods. The dull-grey crystal structure formed by the process bonds more strongly with paint, powder coating, and rubber overmolding processes than other methods. It is a preferred method for coating small, complex-shaped metals, and for smoothing in rough surfaces on items formed with powder metal.
*Eventual corrosion[edit]*


Rusted corrugated steel roof


Although galvanizing will inhibit attack of the underlying steel, rusting will be inevitable, especially if exposed to the natural acidity of rain. For example, corrugated iron sheet roofing will start to degrade within a few years despite the protective action of the zinc coating. Marine and salty environments also lower the lifetime of galvanized iron because the high electrical conductivity of sea water increases the rate of corrosion primarily through converting the solid zinc to soluble zinc chloride which simply washes away. Galvanized car frames exemplify this; they corrode much quicker in cold environments due to road salt. Galvanized steel can last for many years if other means are maintained, such as paint coatings and additional sacrificial anodes. The rate of corrosion in non-salty environments is mainly due to levels of sulfur dioxide in the air.[SUP][9][/SUP]
*Galvanized piping[edit]*

See also: Galvanic corrosion
In the early 20th century, galvanized piping replaced cast iron and lead in cold-water plumbing. Typically, galvanized piping rusts from the inside out, building up plaques on the inside of the piping, causing both water pressure problems and eventual pipe failure. These plaques can flake off, leading to visible impurities in water and a slight metallic taste. The life expectancy of such piping is about 70 years, but it may vary by region due to impurities in the water supply and the proximity of electrical grids for which interior piping acts as a pathway (the flow of electricity can accelerate chemical corrosion). Pipe longevity also depends on the thickness of zinc in the original galvanization, which ranges on a scale from G40 to G210, and whether the pipe was galvanized on both the inside and outside, or just the outside. Since World War II, copper and plastic piping have replaced galvanized piping for interior drinking water service, but galvanized steel pipes are still used in outdoor applications requiring steel's superior mechanical strength.
This lends some truth to the urban myth that water purity in outdoor water faucets is lower, but the actual impurities (iron, zinc, calcium) are harmless. This is not always the case in pre-1986 copper pipe where lead-containing solder was commonly used. In installations where copper pipe has been fitted to replace a section of corroded galvanized pipe, a dielectric fitting, usually a union, must be used to join the two types of pipes; otherwise the presence of water in contact with differing metals creates an electrical current that can cause "galvanic corrosion". In some amateur installations, the failure to use this special fitting has caused the lead in the solder to leach into the drinking water. A common location where this occurs is where a home's copper piping connects to a galvanized steel municipal supply line.
The presence of galvanized piping detracts from the appraised value of housing stock because piping can fail, increasing the risk of water damage. Galvanized piping will eventually need to be replaced if housing stock is to outlast a 50 to 70 year life expectancy, and some jurisdictions[SUP][_which?_][/SUP] require galvanized piping to be replaced before sale. One option to extend the life expectancy of existing galvanized piping is to line it with an epoxy resin.[SUP][_citation needed_][/SUP]
*See also[edit]*



Cathodic protection
Corrugated galvanized iron
Galvanic corrosion
Galvannealed - galvanization and annealing
Rust
Rustproofing
Sendzimir process
Sherardizing


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## سيد صلاح الصاوى (2 يوليو 2014)

http://www.galvanizeit.org/

http://www.galvinfo.com/


وهذه المواصفات

http://www.galvinfo.com/references_and_standards.htm


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## سيد صلاح الصاوى (2 يوليو 2014)

الجَلْفنة عملية طلاء بعض الفلزات، كالحديد، والفولاذ، بطبقة خفيفة مانعة من الزنك أو سبيكة الزنك. هذه الطبقة تحمي الفلزات من التآكل (التلف الكيميائي). يساعد الزنك في منع التآكل لأنه يتفاعل مع كثير من المواد الكيميائية بسهولة أكبر من تفاعله مع الحديد. فعلى سبيل المثال، عندما يتفاعل الحديد مع أكسجين الهواء، يشكل أكسيد الحديد (الصدأ). وعلى كل حال، فإذا تمت جلفنة الحديد، فإن الزنك يحمي الحديد بتفاعله مع الأكسجين، مكونًا أكسيد الزنك قبل أن يتكون الصدأ.

الفولاذ من أكثر الفلزات التي تجلفن بالزنك. وتسمى إحدى أبسط الطرائق وأكثرها استخدامًا فى عملية الطلاء باستخدام الزنك، جلفنة الغمس ـ الساخن. وتشمل هذه الطريقة غمس الفولاذ فى حمام ساخن به سائل من الزنك. وفي بعض الحالات، يخلط صانعو الفولاذ بعض الفلزات الأخرى، مثل الألومنيوم والأنتيمون والكدميوم والقصدير مع الزنك. ويضيف الصُناع مثل هذه الفلزات لتحسين المظهر أو لحماية الطلاء. يغمس الدلاء الفلزي، وفلزات صغيرة مشابهة فى حمام من الزنك ويتم جلفنتها بالزنك واحداً بعد الآخر.

ويجلفن صانعو الفولاذ قطعاً كبيرة من ألواح الصلب (الفولاذ) بالزنك، وذلك بتمريرها باستمرار خلال حمام من الزنك ثم لفها. وتشكل هذه الطريقة من طرائق الجلفنة بالزنك سمكاً مقداره 0,08 ملم. وتضغط أو تكبس ألواح الفولاذ التي تجلفن بهذه الطريقة لتشكل هياكل السيارات، وأسطح المنازل المصنوعة من الفولاذ. انظر: الحديد والفولاذ.

وهناك طريقة أخرى أقل استخداماً في جلفنة الفولاذ بالزنك تدعى الجلفنة بالكهرباء. وتشمل هذه العملية وضع الفولاذ في محلول من كبريتات الزنك والماء. وعند مرور التيار الكهربائي في المحلول يشكل الزنك طبقة خفيفة على سطح الفولاذ. تستخدم الجلفنة بالكهرباء (الطلاء بالكهرباء) أساسًا في جلفنة قطعة متصلة من الفولاذ. ا


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## سيد صلاح الصاوى (2 يوليو 2014)

الغلفنة أو الجَلْفنة (بالإنجليزية: Galvanization) هي عملية طلاء بعض الفلزات، كالحديد، الفولاذ، بطبقة خفيفة مانعة من الزنك أو سبيكة الزنك. هذه الطبقة تحمي الفلزات من التآكل (التلف الكيميائي). يساعد الزنك في منع التآكل لأنه يتفاعل مع كثير من المواد الكيميائية بسهولة أكبر من تفاعله مع الحديد. فعلى سبيل المثال، عندما يتفاعل الحديد مع أكسجين الهواء، يشكل أكسيد الحديد (الصدأ). فإذا تمت جلفنة الحديد، فإن الزنك يحمي الحديد بتفاعله مع الأكسجين، مكونًا أكسيد الزنك قبل أن يتكون الصدأ.ويعد الفولاذ من أكثر الفلزات التي تجلفن بالزنك. وتسمى إحدى أبسط الطرق وأكثرها استخدامًا في عملية الطلاء باستخدام الزنك، جلفنة الغمس الساخن. وتشمل هذه الطريقة غمس الفولاذ في حمام ساخن به الزنك المنصهر. وفي بعض الحالات، يخلط صانعوا الفولاذ بعض الفلزات الأخرى، مثل الألومنيوم الأنتيمون الكدميوم القصدير مع الزنك. ويضيف الصُناع مثل هذه الفلزات لتحسين المظهر أو لحماية الطلاء. يغمس الأدوات المعدنية ، وأدوات معدنية صغيرة مشابهة في حمام من الزنك ويتم جلفنتها بالزنك واحداً بعد الآخر.وهناك طريقة أخرى أقل استخداماً في جلفنة الفولاذ بالزنك تدعى الجلفنة بالكهرباء. وتشمل هذه العملية وضع الفولاذ في محلول من كبريتات الزنك والماء في وجود لوح من الزنك. وعند توصيل مصدر كهربائي من الخارج بين الأداة المعدنية المراد طلاؤها ولوح الزنك، فتتجه أيونات الزنك في المحلول وتترسب على سطح الأداة وتشكل طبقة رقيقة على سطح الأداة.استخدامات الجلفنة[عدل]تستخدم الجلفنة عادة لتزيين الأدوات المعدنية أو بغرض حفظها من الصدا. فبالنسبة إلى التزيين فهو يستخدم لتجميل أوعية وادوات، مثل جلفنة البلاستيك وطلاء الكروم للأثاث المصنوع من أنابيب حديدية، ولطلاء عجلات السيارات وكذلك لطلاء الحلي وأدوات الأكل بالذهب.أما الستخدام الآخر للجلفنة فهو بغرض حفظ الأدوات الحديدية من الصدأ ومن التآكل أو بغرض صناعة المحفزات الكيميائية أو تحسين التوصيل الكهربائي أو الخفض من قوى الاحتكاك للأجزاء المعدنية المتحركة. ومن الامثلة على ذلك طلاء المسامير والقلاووظ بالزنك، طلاء أجزاء الآلات بالكروم، وصناعة المحفزات مواسطة طلاء البلاتين أو النيكل للصناعات الكيميائية و لخلايا الوقود التي تنتج الكهرباء، وكذلك لطلاء أدوات الجراحة الطبية.تطلى معظم الوصلات الكهربائية المصنوعة من النحاس عادة بالزنك بطريقة الجلفنة. وبغرض منع مادة الأداة المراد جلفنتها من الاختلاط بالزنك أثناء عملية الجلفنة فيسبق ذلك طلاؤها بالنيكل أو النحاس.​كذلك يتم إنتاج الأقراص المضغوطة الضوئية (CDs/DVDs) بواسطة تقنية الجلفنة


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## سيد صلاح الصاوى (2 يوليو 2014)

معلومات عن الجلفنة


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## سيد صلاح الصاوى (2 يوليو 2014)

السلام عليكم

المهندس نادر خليل قدم مجموعة طيبة جدا من المواضيع حول هذا الأمر

hot dip galvanization

الجلفنه بالغمر علي الساخن

الجلفنة بالغمر علي الساخن(بوربوينت)


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## سيد صلاح الصاوى (2 يوليو 2014)

السلام عليكم ورحمة الله وبركاته
هذا الكتاب مفيد جدا :
Corrosion Prevention and Protection: Practical Solutions
By *Edward Ghali, Vedula S. Sastri, M. Elboujdaini

http://ifile.it/8dzwic9/047002402X.zip*


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## سيد صلاح الصاوى (2 يوليو 2014)

السلام عليكم ورحمة الله وبركات

جلفنة الصلب بطريقة الغمر على الساخن Hot dip Galvanizing

في البداية يجب علينا ان نحضر القطع الفولاذية المراد جلفنتها و ذلك عن طريق :

تحضير و تنظيف السطح قبل عملية الجلفنة و يتم بطريقتين ممكن ان تستخدم كل واحدة منفردة او مع بعض


بتركيز عالي نسيبا


بعد التنظيف يمكن ان تشطف القطع بالماء لازالة الاثر الحمضي و من ثم تعريضها ل flux
وهو عبارة عن zinc ammonium chloride flux لمنع حدوث اكسدة على السطح


ثم يتم تغطيس القطع في حوض من الزنك المصهور (درجة الحرارة ما بين 460 و 440 درجة موية)
زمن التغطيس من دقيقتين وحتى 5 دقائق حسب سماكة الجلفنة المرادة

بعد عملية الجلفنة ممكن ان يتم تبريد القطع في الماء او محلول Sodium dichromate
لتخفيف ظهور طبقة بيضاء على سطح القطع 1- تغطيس القطع في محلول قاعدي Caustic cleaning عادة ما يستخدم Caustic soda 2- تغطيس القطع في محلول حمضي Acid pickling و يمكن استخدام حمض sulfuric Acid او hydrochloric acid بتركيز متوسط الى قوي حسب حالة القطع المراد جلفنتها


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## سيد صلاح الصاوى (2 يوليو 2014)

*Hot dip galvanizing –​Process, applications, properties
*​


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## سيد صلاح الصاوى (2 يوليو 2014)

Galvanize It Seminar - PowerPoint PPT Presentation

see attached link

PPT â€“ Galvanize It Seminar PowerPoint presentation | free to download


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## سيد صلاح الصاوى (2 يوليو 2014)

American Galvanizers Association Videos

https://www.youtube.com/user/AGAGalvanizeIt/videos


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## سيد صلاح الصاوى (2 يوليو 2014)

American Galvanizers Association site


see attached link

American Galvanizers Association


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## سيد صلاح الصاوى (2 يوليو 2014)

[h=2]Galvanising process[/h]Galvanising provides outstanding corrosion performance in a wide variety of environments. The galvanising process creates a durable, abrasion-resistant coating of metallic zinc and zinc-iron alloy layers which are bonded metallurgically to the steel and completely covers the item providing a number of significant advantages.It provides outstanding toughness, resistance to mechanical damage, slows corrosion to about one sixteenth that of steel and a standard minimum coating thickness is applied even to sharp corners to provide a sound and continuous coating.​[h=3]The galvanising process[/h][h=4]Surface Preparation[/h]Preparation is vital to high-quality galvanising. Fero Galv and Fero Blast work together to ensure the preparation for galvanising is perfect. Epoxies, powder coating and other paints must be removed mechanical cleaning such as shot or sand blasting.​[h=4]Caustic Cleaning[/h]The first cleaning step is caustic cleaning or degreasing in a hot alkali solution to remove contaminates like dirt, grease and oil from the metal surface prior to the galvanising process.​[h=4]Acid Pickling[/h]Scale, rust, residual paint and other surface contaminates are removed from the steel by acid cleaning or pickling in hydrochloric acids followed by rinsing.​[h=4]Fluxing[/h]The acid-cleaned steel is then immersed in a flux solution or zinc ammonium chloride and wetting agents to remove the oxide film, which forms on highly reactive steel surfaces following acid cleaning and prevents further oxidisation. This process also heats the steel to between 60-80 degrees Celsius to prepare it for the high temperatures of hot-dipping in the zinc bath.​[h=4]Hot-dip galvanising[/h]The molten zinc is heated to about 450 degrees Celsius. When the steel is immersed in the galvanising bath at a controlled rate, the steel surface is coated by the molten zinc resulting in a reaction between the zinc and the formation of a series of zinc-alloy layers. This process takes about 10-15 mins, longer for larger items, and the resulting zinc-alloy layers are actually harder than the base steel. As the item is removed, again at a controlled rate, the molten zinc solidifies to form the outer zinc coating.​[h=4]Quenching[/h]After galvanising, the steelwork is immediately dipped is a quench solution which contains additives to prevent the formation of wet storage staining or "white rust" occurring. This process also cools the steelwork in order to facilitate the efficient movement of steel products. Some products can be air-cooled if required.​[h=4]Fettling[/h]Then any remaining excess drips and drags are removed.​[h=4]Galvanising small components (spinning)[/h]Small components are loaded into baskets for galvanising. Once removed from the molten zinc the spinning baskets are centrifuge spun to remove excess zinc.​[h=3]Coating thickness[/h]The total zinc coating mass or coating thickness of galvanized steel depends mainly on the mass and thickness of the steel being galvanised.*Other factors influencing coating thickness include:*​[h=4]Surface condition:[/h]The process of grit blasting steel before galvanising increases the surface area and results in greater zinc-alloy growth during galvanising, producing a thicker coating, but also a rougher finish of the surface.​[h=4]Composition of steel:[/h]Silicon and phosphorous content can have a major effect on the structure, appearance and properties of galvanised coatings.​[h=4]Silicon:[/h]Certain levels of silicon content will result in excessively thick galvanised coatings. Steels with silicon content in the range of 0.04-0.14 per cent result in excessive growth of zinc-iron alloys on steel surfaces and will generally have a dull grey appearance. Growth rates are less for steels containing between 0.15 and 0.22 per cent and increase again with greater silicon levels.​[h=4]Phosphorous[/h]The presence of phosphorous above 0.5 per cent produces an increase in the coating growth. When present in combination with silicon excessively thick galvanised coatings can be produced.​


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## سيد صلاح الصاوى (3 يوليو 2014)

*Inspection cours - Galvanizing Processe*

[h=1]Galvanizing Process[/h]The term hot-dip galvanizing is defined as the process of immersing iron or steel in a bath of liquid zinc to produce a corrosion resistant, multi-layered coating of zinc-iron alloy and zinc metal. The coating is produced as the result of a metallurgical reaction between the liquid zinc and the iron in the steel. The coating forms an equal thickness on all surfaces immersed in the galvanizing kettle. This process, similar to the one seen in _Figure 1_, has been in use since 1742 and has provided long-lasting, maintenance-free corrosion protection at a reasonable cost for many years. The three main steps in the hot-dip galvanizing process are surface preparation, galvanizing, and post-treatment, each of which will be discussed in detail.




Figure 1: Model of the Hot-Dip Galvanizing Process Steel structures with visible evidence of corrosion are pictured in the series of photos in _Figure 2_. Rust and corrosion can be expensive for business owners and taxpayers because buildings, roads, and bridges, without sufficient corrosion protection, may need to be repaired often or even rebuilt.
The process is described in more detail later in this section. It is inherently simple, and this simplicity is a distinct advantage over other corrosion protection methods.



Figure 2: Corroding Steel Structures


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Surface Preparation[/h]



Figure 3: Hanging of Steel Products The first step in the hot-dip galvanizing process is intended to obtain the cleanest possible steel surface by removing all of the oxides and other contaminating residues. This is achieved by first hanging the steel using chains, wires, or specially designed dipping racks, as seen in _Figure 3_, to move the parts through the process. There are three cleaning steps to prepare the steel for galvanizing.
[h=3]Degreasing/Caustic Cleaning[/h]First the steel is immersed in an acid degreasing bath or caustic solution in order to remove the dirt, oil, and grease from the surface of the steel. After degreasing the steel is rinsed with water.



Figure 4: The Pickling Tank [h=3]Pickling[/h]Next the steel is immersed in an acid tank filled with either hydrochloric or sulfuric acid, as seen in _Figure 4_, which removes oxides and mill scale in a process called “pickling.” Once all oxidation has been removed from the steel, it is again rinsed with water and sent to the final stage of the surface preparation.
[h=3]Fluxing[/h]The purpose of the flux is to clean the steel of all oxidation developed since the pickling of the steel and to create a protective coating to prevent the steel from any oxidizing before entering the galvanizing kettle. One type of flux is contained in a separate tank, is slightly acidic, and contains a combination of zinc chloride and ammonium chloride. Another type of flux, top flux, floats on top of the liquid zinc in the galvanizing kettle, but serves the same purpose.
After being immersed in the degreasing, pickling, and fluxing tanks, the surface of the steel is completely free of any oxides or any other contaminants that might inhibit the reaction of the iron and liquid zinc in the galvanizing kettle.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Galvanizing[/h]



Figure 5: Hot-Dip Galvanizing Kettle Once the steel has been completely cleaned, it is ready for immersion in the liquid zinc. The galvanizing kettle contains zinc specified to ASTM B 6, a document that specifies any one of three different grades of zinc that are each at least 98% pure. Sometimes other metals may be added to the zinc melt in order to promote certain desirable properties in the galvanized coating.
The galvanizing kettle, like the one seen in _Figure 5_, is typically operated at a temperature ranging from 820-860 F (438-460 C), at which point the zinc is in its liquid state. The steel products are immersed into the galvanizing kettle and remain in the kettle until the temperature of the steel has reached the temperature required to form a hot-dip galvanized coating. Once the interdiffusion reaction of iron and zinc is completed, the steel product is withdrawn from the zinc kettle. The entire dip usually lasts less than ten minutes, depending upon the thickness of the steel.
The coating, as seen in the micrograph in _Figure 6_, is typical for low silicon steels with silicon impurities less than 0.04% and where the thickness of the coating is limited by the interdiffusion of iron and zinc.



Figure 6: Photomicrograph of the galvanized coating [h=3]Post-Treatment[/h]



Filing Zinc Drips When the steel is removed from the galvanizing kettle, it may receive a post-treatment to enhance the galvanized coating. One of the most commonly used treatments is quenching. The quench tank contains mostly water but may also have chemicals added to create a passivation layer that protects the galvanized steel during storage and transportation. Other finishing steps include removal of zinc drips, or icicles, by grinding them off.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Time to First Maintenance[/h]The estimated time to first maintenance for a hot-dip galvanized coating that experiences common atmospheric exposure can be seen in _Figure 7_. Time to first maintenance is defined as the time to 5% rusting of the substrate steel. The time to first maintenance of hot-dip galvanized steel is directly proportional to the zinc coating thickness.




Figure 7: Time to First Maintenance Chart for Hot-Dip Galvanized Coatings ​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Other Corrosion Protection Systems[/h]There are many other types of corrosion protection, such as coating steel with oil, grease, tar, asphalt, polymer coatings or paints, or corrosion protection materials such as stainless and weathering steel, sacrificial anodes, plating systems and impressed current systems. These are some of the most commonly used corrosion protection materials and systems and are sometimes used together with hot-dip galvanized steel. Most of these materials rely on barrier protection, while some of them rely on cathodic properties to prevent corrosion of the steel. The most effective type of corrosion protection that provides both barrier and cathodic protection is hot-dip galvanizing.
There are also a wide variety of zinc coatings used for corrosion protection. Many people use “galvanizing” to describe all of these coatings, but each has its own unique characteristics and performance. These coatings have several applications based on their properties and respective thicknesses. The corrosion protection offered by a zinc coating is linearly related to its coating thickness. The most commonly used coatings are hot-dip galvanized, metallized, zinc-rich paint, galvannealed or galvanized sheet, and electroplated. The relative thickness for each of these zinc coatings can be seen in the photomicrograph (_Figure 8_). Below is a brief explanation of each type of zinc coating.



Figure 8: Photomicrogrpah of Zinc Coatings’ Thicknesses [h=3]Metallizing[/h]Metallizing is the general name for the technique of spraying a metal coating on the surface of non-metallic or metallic objects. This process is accomplished by feeding zinc in either wire or powder form into a heated gun, where it is melted and sprayed onto the surface to be coated using combustion gases and/or auxiliary compressed air to provide the necessary velocity. The limitations of this process include a difficulty in reaching recesses, cavities, and hollow spaces, even coating thickness and cost.
[h=3]Zinc-Rich Paint[/h]Zinc-rich paint is applied to a clean, dry steel surface by either a brush or spray and usually contains an organic binder pre-mix. Paints containing zinc dust are classified as organic or inorganic, depending on the binder that they contain, and are discussed in more detail later in this course.
[h=3]Continuous Galvanizing[/h]



Figure 9: Continuous Galvanizing Plant The continuous galvanizing process is a hot-dip process where a steel sheet, strip, or wire is cleaned, pickled, and fluxed on a processing line approximately 500 feet (154 m) in length, and running at speeds between 100 to 600 feet per minute (30 to 185 m per minute). In the coating of a steel sheet or strip, the galvanizing kettle contains a small amount of aluminum, which suppresses the formation of the zinc-iron alloys, resulting in a coating that is mostly pure zinc. A post-galvanizing, in-line heat treatment process known as galvannealing can also be used to produce a fully alloyed coating. Galvannealing is usually ordered by those wanting to paint over the zinc surface because the presence of alloy layers on the steel surface promotes paint adhesion. A photo of a continuous galvanizing plant is seen in _Figure 9_ and the common plant setup is shown in _Figure 10_.



Figure 10: Example of a Continuous Process [h=3]Electroplating[/h]The electroplating process, or zinc-plated coating, has a dull gray color, a matte finish, and a thin coating that ranges up to one mil (25 µm) thick. This very thin coating restricts the use of zinc-plated products to indoor exposures. The specification ASTM B 633 lists the classes of zinc-plated steel coatings as Fe/Zn 5, Fe/Zn 8, Fe/Zn 12, and Fe/Zn 25, where Fe represents iron and Zn represents zinc, while the number indicates the coating thickness in microns. The main uses for this type of coating include screws, light switch plates, and other small products or fasteners.

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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Galvanizing Standards[/h]There are certain specifications that have been developed for hot-dip galvanizing in order to produce a high-quality coating. The most commonly used specifications design engineers and fabricators should become familiar with in order to promote a high-quality coating and ensure their steel design is suitable for hot-dip galvanizing are:


*ASTM A 123/A 123M:* _Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products_
Single pieces of steel or fabrications with different types of steel products
*ASTM A 153/A 153M:* _Standard Specification for Zinc Coating (Hot-Dip) on Iron and Hardware_
Fasteners and small products that are centrifuged after galvanizing to remove excess zinc
*ASTM A 767/A 767M:* _Standard Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement_
Reinforcing steel or rebar
*ASTM A 780:* _Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings_
Touch-up procedures for coating bare spots on an existing hot-dip galvanized product
Other commonly used specifications in the hot-dip galvanizing industry include:


*ASTM A 143/A 143M:* _Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement_
*ASTM A 384/A 384M:* _Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies_
*ASTM A 385/A 385M:* _Standard Practice for Providing High-Quality Zinc Coatings (Hot-Dip)_
*ASTM B 6:* _Standard Specification for Zinc_
*ASTM D 6386:* _Standard Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Paint_
*ASTM E 376:* _Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy-Current (Electromagnetic) Examination Methods_
*CAN/CSA G 164:* _Hot-Dip Galvanizing of Irregularly Shaped Articles_
*ISO 1461* _Hot-Dip Galvanized Coatings on Fabricated Iron and Steel _.
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## سيد صلاح الصاوى (3 يوليو 2014)

*ASTM A 123 for Structural Steel Products*




Figure 11: Single Fabrication with Multiple Material Categories The ASTM A 123/A 123M specification covers individual steel pieces as well as assemblies of various classes of material. The four material categories covered in ASTM A 123/A 123M include structural steel and plates, strips and bars, pipes and tubing, and wires. A fabrication can have more than one material category such as a frame assembly. Any combination of these products can be assembled into a single fabrication and then can be hot-dip galvanized, as seen in _Figure 11_.
It is the responsibility of the designer and fabricator to ensure the product has been properly designed and built before the hot-dip galvanizing process. The galvanizer should be made aware of any necessary special instructions or requests in advance of shipping the materials to the galvanizing plant. These requests should be stated on the purchase order for the hot-dip galvanizing.
It is the responsibility of the galvanizer to ensure compliance with the specifications as long as the product has been designed and fabricated in accordance with the referenced specifications. However, if the galvanizer has to perform additional work in order to prepare the product for hot-dip galvanizing, such as drilling holes to facilitate drainage or venting, it must be approved by the customer. Once the material has been hot-dip galvanized, it can be fully inspected at the galvanizing plant prior to shipment.
Any materials rejected by the inspectors for reasons other than embrittlement may be stripped, regalvanized, and resubmitted for inspection. The ASTM specifications A 143/A 143M, ASTM A 384/A 384M, and ASTM A 385 provide guidelines for preparing products for hot-dip galvanizing. The requirements listed in ASTM A 123/A 123M include coating thickness, finish, appearance, and adherence. These are each defined below and discussed in more detail later in this course.
*ASTM A 123/A 123M Requirements*



*Coating Thickness / Weight* – dependent upon material category and steel thickness
*Finish* – continuous, smooth, uniform
*Appearance* – free from uncoated areas, blisters, flux deposits and gross dross
inclusions as well as having no heavy zinc deposits that interfere with intended use
*Adherence* – the entire coating should have a strong adherence throughout the service
 life of galvanized steel
The hot-dip galvanized coating is intended for products fabricated into their final shape that will be exposed to corrosive environmental conditions. Once a product has been hot-dip galvanized, any further fabrication, which very rarely occurs, may have negative effects on the corrosion protection of the coating. The coating grade is defined as the required thickness of the coating and is given in microns. All coating thickness requirements in specification ASTM A 123/A 123M, as seen in _Tables 1 & 2_, are minimums; there are no maximum coating thickness requirements in either specification.



Table 1: Minimum Average Coating Thickness Grade by Material Category (From ASTM A123)



Table 2: Coating Thickness Grade (From ASTM A 123) The time to first maintenance of hot-dip galvanized steel is directly proportional to the thickness of the hot-dip galvanized coating. With all other variables held constant, the thicker the zinc coating, the longer the life of the steel. The aim of the finish and appearance requirements is to ensure no coatings have problem areas that are deficient of zinc or have surface defects that would interfere with the intended use of the product. In addition, the coating should have a strong adherence throughout the service of the hot-dip galvanized steel.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]ASTM A 153 for Hardware[/h]



Figure 12: Galvanized Fasteners 
The specification ASTM A 153/A 153M applies to hardware products such as castings, fasteners, rolled, pressed and forged products, and miscellaneous threaded objects that will be centrifuged, spun, or otherwise handled to remove the zinc, as seen in _Figure 12_.
The requirements for ASTM A 153/A 153M are very similar to those reported earlier for ASTM A 123/A 123M, except for the addition of threaded products and embrittlement requirements.
[h=3]ASTM A 153/A 153M Requirements[/h]

*Coating Thickness/Weight* – depends on the material category and steel thickness, values are listed in _Table 3_
*Threaded Products* – areas with threads are not subject to the coating
thickness requirement
*Finish* – continuous, smooth, uniform
*Embrittlement* – high tensile strength fasteners (>150ksi) and castings
 can be subject to embrittlement
*Appearance* – free from uncoated areas, blisters, flux deposits and
gross dross inclusions as well as having no heavy zinc deposits that interfere with intended use
*Adherence* – the entire coating should have a strong adherence
 throughout the service life of hot-dip galvanized steel

There are fabrication steps that may impair the corrosion protection of the hot-dip galvanized coating, however, flaking or damage to the coating because of this is not case for rejection. In all cases, good steel selection results in the formation of a higher quality coating and finish on the product. The corrosion protection coating for threaded products is applied after the product has been fabricated and further fabrication may compromise the corrosion protection system. The one exception to this rule is the internal threads of a nut that should be over-tapped after the coating is applied in order to accommodate the coating thickness change on the thread of the bolts. In this case, the zinc on the bolt threads provides the corrosion protection to the uncoated threads in the nut.
There are certain fabrication techniques that can induce stresses into the steel and lead to brittle failure. There are precautions given in ASTM A 143/A 143M that should be taken in order to prevent embrittlement. In addition, selecting steels with appropriate chemistries can help prevent embrittlement of malleable castings. A reproduction and summary of the table given in ASTM A 153/A 153M, which is seen in _Table 3_, gives the different classes of products and the minimum coating thickness required by the specification.



Table 3: Minimum Average Coating Thickness by Material Class (From ASTM A 153)​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]ASTM A 767 for Reinforcing Steel[/h]The specification ASTM A 767/A 767M is applicable exclusively to the hot-dip galvanizing of reinforcing steel, otherwise known as rebar, as seen in _Figure 13_, and is applicable to all types of rebar, both smooth and deformed. However, wire is not included.



Figure 13: Hot-Dip Galvanized Rebar The requirements in ASTM A 767/A 767M are also intended to produce a high quality zinc coating for corrosion protection.
[h=3]ASTM A 767/A 767M Requirements[/h]

*Identity* – the galvanizer is responsible for consistent material tracking if
necessary
*Coating Thickness/Weight* – material category and steel thickness
*Chromating* – to prevent reaction between cement and recently
galvanized material
*Finish* – continuous, smooth, and uniform
*Appearance* – free from uncoated areas, blisters, flux deposits and
 gross dross inclusions as well as having no heavy zinc deposits that interfere with intended use
*Adherence* – should be tightly adherent throughout intended use of the
 product
*Bend Diameters* – flaking and cracking due to fabrication after the hot-
dip galvanizing process are not rejectable
Once rebar is delivered to be hot-dip galvanized, it is the galvanizer’s responsibility to track and maintain the identity of the product throughout the hot-dip galvanizing process until shipment of the finished product. Again, the analogous coating requirements in the areas of coating thickness, finish, and adherence are present in ASTM A 767/A 767M. However, this single product specification introduces a few new requirements that apply solely to hot-dip galvanized rebar. In ASTM A 767/A 767M, the coating requirement is given in “mass of the zinc coating per surface area”. A summary of the table given in ASTM A 767/A 767M and the minimum required coating thickness / weight of the classes is seen in _Table 4_.



Table 4: Mass of Zinc Coating (From ASTM A 767) This specification also introduces a new requirement to the galvanized coating known as chromating. Newly galvanized steel can react with wet cement and potentially form hydrogen gas as a product. As this evolved hydrogen gas travels through the concrete matrix toward the surface, voids can be created which weaken the bonding with the concrete or disturb the smoothness of the concrete surface. In order to help prevent and suppress this reaction, hot-dip galvanized rebar is dipped into a weak chromate quench solution after being removed from the galvanizing kettle.
The finish requirement for rebar is along the same lines as the finish requirements given in specifications ASTM A 123/A 123M and A 153/A 153M. The coating is intended for corrosion protection, so deficiencies that affect the coating’s corrosion performance are grounds for rejection. In addition, since rebar is handled frequently during its installation, any tears or sharp spikes that make the material dangerous to handle are grounds for rejection.
Rebar is commonly bent prior to the hot-dip galvanizing process. The table below gives recommendations for bend diameters based upon the bare steel bar diameter before coating. Steel reinforcing bars that are bent cold prior to hot-dip galvanizing should be fabricated to a bend diameter equal to or greater than the specified values. However, steel reinforcing bars can be bent to diameters tighter than specified in _Table 5_ providing they are stress relieved at a temperature of 900 to 1050 F (480 to 560 C) for one hour per inch (25 mm) of diameter.



Table 5: Minimum Finished Bend Diameters (From ASTM A 767) ​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Other Galvanizing Standards[/h]There are Canadian and international specifications that could be used to specify hot-dip galvanizing on a project. The differences in these specifications and the ASTM specifications are minimal, and for the most part, only differ slightly in the minimum coating thickness/weight required for each type and thickness of product being hot-dip galvanized.
[h=2]Other Specifications for Hot-Dip Galvanizing (Taken from CAN/CSA and ISO Standards)[/h][h=3]CAN/CSA-G164 Hot Dip Galvanizing of Irregularly Shaped Articles[/h]Scope


This standard specifies the requirements for zinc coating (galvanizing) by the hot-dipping process on iron and steel products made from rolled, pressed, or forged shapes such as structural sections, plates, bars, pipes, or sheets 1 mm thick or thicker.
Applies to both unfabricated and fabricated products such as assembled steel products, structural steel fabrications, large hollow sections bent or welded before galvanizing, and wire work fabricated from uncoated steel wire.
Applies to steel forgings and iron castings that are to be galvanized separately or in batches.
Does not apply to continuous galvanizing of chain link fence fabric, wire, sheet, and strip.
Does not apply to pipe and conduit that are normally hot dip galvanized by a continuous or semicontinuous automatic process.
The values stated in SI units are to be regarded as the standard. The values in parentheses are imperial units and are included for information only.
[h=3]ISO 1461 Hot Dip Galvanized Coatings on Fabricated Iron and Steel Articles[/h]Scope: This Standard specifies the general properties of and methods of test for coatings applied by hot dipping in zinc (containing not more than 2% of other metals) on fabricated iron and steel articles.
It does not apply to:


Sheet and wire continuously hot dip galvanized;
Tube and pipe hot dip galvanized in automatic process;
Hot dip galvanizing products for which specific standards exist and which may include additional requirements or requirements different from those of this European Standard.
After-treatment/overcoating of hot dip galvanized articles is not covered by this standard.
*NOTE* Individual product standards can incorporate this standard for the coating
by quoting its number, or may incorporate it with modifications specific to the product.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Types of Inspection[/h]In this section, the type of inspections performed on hot-dip galvanized steel will be discussed. The various inspections are used to verify the necessary specifications for the galvanized product are met. These techniques for each test method are specified in ASTM A 123/A 123M, A 153/A 153M, or A 767/A 767M, depending upon the type of product being inspected. The most common inspections, listed below, range from a simple visual inspection to more sophisticated tests to determine embrittlement or adhesion.


*Coating Thickness* – magnetic gauges, optical microscopy
*Coating Weight* – weigh-galvanize-weigh, and weigh-strip-weigh
*Finish and Appearance* – visual inspection
*Additional Tests*
*Adherence* – stout knife
*Embrittlement* – similar bend radius, sharp blow, and steel
angle
*Chromating* – spot test
*Bending* – minimum finished bend diameter table

*Sampling*
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Coating Thickness[/h]The term coating thickness refers to the thickness of zinc applied to steel, while coating weight refers to the amount of zinc applied to steel for a given surface area. Two different methods are used in order to measure the coating thickness of hot-dip galvanized steel.
The first method to measure coating thickness involves using magnetic thickness gauges. There are three different types of magnetic thickness gauges and all can be used quite easily in the galvanizing plant or in the field.



Figure 14: Pencil-Style Gauge The first type of magnetic thickness gauge is very small and utilizes a spring-loaded magnet encased in a pencil-like container, as seen in _Figure 14_. The tip of the gauge is placed on the surface of the steel and is slowly pulled off in a continuous motion. When the tip of the gauge is pulled away from the surface of the steel, the magnet, near the tip, is attracted to the steel. A graduated scale indicates the coating thickness at the instant immediately prior to pulling the magnet off the surface of the steel. The accuracy of this gauge requires it to be used in the true vertical plane because, due to gravity, there is more error associated with measurements taken in the horizontal plane or overhead positions. The measurement should be made multiple times because the absolute accuracy of this type of gauge is below average and it is difficult to determine the true coating thickness when only one reading is taken.



Figure 15: Banana Gauge A banana gauge, as seen in _Figure 15_ is the second type of thickness gauge. With this gauge, coating thickness measurements are taken by placing the rubber magnet housing on the surface of the product with the gauge held parallel to the surface. A scale ring is rotated clockwise to bring the tip of the instrument in contact with the coated surface and rotated counter-clockwise until a break in contact can be heard and felt. The position of the scale ring when the magnetic tip breaks from the coated surface displays the coating thickness. This type of gauge has the advantage of being able to measure coating thickness in any position, without recalibration or interference from gravity.



Figure 16: Electronic/Digital Thickness Gauge The electronic or digital thickness gauge, as seen in _Figure 16_ is the most accurate and arguably, the easiest thickness gauge to operate. The electronic thickness gauge is operated by simply placing the magnetic probe onto the coated surface and then a digital readout displays the coating thickness. Electronic gauges have the advantage of not requiring recalibration with probe orientation, but do require calibration with shims of different thicknesses in order to verify the accuracy of the gauge at the time it is being used. These shims are measured and the gauge is calibrated according to the thickness of the shim, and then this process is repeated for shims of different thicknesses until the gauge is producing an accurate reading in all ranges of thickness.
[h=3]ASTM E 376[/h]The specification ASTM E 376 contains information for measuring coating thickness using magnet or electromagnetic current. It also provides some tips for obtaining measurements with the greatest accuracy, as well as describing how the physical properties, the structure, and the coating can interfere with the measurement methods. The requirements for ASTM E 376, as seen below, are intended to make the coating thickness measurements using magnet or electromagnetic current as accurate as possible.
*ASTM E 376 Requirements*


Measurements on large products should be made at least four inches from the edge to avoid edge effects
Measurement readings should be as widely dispersed as possible
There are some general guidelines, as seen below, for reducing error and ensuring the most accurate readings are being collected when using magnetic thickness gauge instruments.
*Guidelines for Reducing Error*


Recalibrate frequently, using non-magnetic film standards or shims above and below the expected thickness value
Readings should not be taken near an edge, a hole, or inside corner
Readings taken on curved surfaces should be avoided if possible
Test points should be on “regular areas” of the coating
Take at least five readings to obtain a good, “true” value which is representative of the whole sample




Figure 17: Optical Microscopy The second method used to measure the coating thickness involves optical microscopy, as seen in _Figure 17_. This is a destructive technique and is typically only used for inspection of the coating of single specimen samples that have failed magnetic thickness readings or for research studies. Since it is not a common method, the accuracy is highly dependent on the expertise of the operator.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Coating Weight[/h]The term coating weight refers to the amount of zinc applied to a product for a given surface area. Two different methods can be used to measure the coating weight of hot-dip galvanized steel.



The first method to measure the coating weight involves using a process called weigh-galvanize-weigh, and is only appropriate for single specimen samples. The zinc coating weight from this technique is underestimated because the actual coating is made up of both iron and zinc and this method will only measure the added zinc weight in the coating. In addition, it can be very difficult to measure and calculate the surface area of a complex steel fabrication, and this makes coating weight values even less accurate.
Weigh-strip-weigh is the second method used to measure coating weight, and again is only appropriate for single specimen samples. This method is destructive since it removes the hot-dip galvanized coating during the measurement. This process involves first weighing the specimen, stripping it of all zinc coating that was added, and then weighing it again. The difference in the weights is then equal to the amount of coating added during the galvanizing process. However, this method is usually only used on very small products like nails, and can be inaccurate because when the coating is stripped there may be some base metal stripped along with the coating. This means that there may be extra iron included in the weight measurement, making for a higher than actual zinc coating weight.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Finish & Appearance[/h]



The inspection of finish and appearance is done with an unmagnified visual inspection. This inspection is performed by fully observing all parts and pieces of a hot-dip galvanized product to ensure all necessary components and specifications have been met. It is done in order to observe surface conditions, both inside and out, and check all contact points, as well as welds, junctions, and bend areas.
[h=3]Appearance[/h]The appearance of the hot-dip galvanized coating can vary from piece to piece, and even section to section of the same piece. There are a number of reasons for the non-uniform appearance, but it is important to note appearance has no bearing on the corrosion protection of the galvanized piece. This section will overview the resons for differences in appearance.
[h=3]Finish[/h]This section will review a number of possible surface defects visible on the galvanized coating. Some of these surface defects are rejectable, as they will seriously lower the corrosion protection, while others have little or no effect on the corrosion performance and are acceptable.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Different Appearances[/h]The appearance of hot-dip galvanized steel immediately after galvanizing can be bright and shiny, spangled, matte gray, or a combination of these. There are a number of reasons for the difference in appearance, as explored here, but regardless if the piece is shiny or dull, the appearance has no effect on the corrosion performance. And in time after exposure to the environment, all galvanized coatings will take on a uniform matte gray appearance.
[h=2]Reasons for Different Appearances[/h][h=3]Steel Chemistry[/h]The most common reason for galvanized steel to have different appearances is the chemistry of the steel pieces. There are two elements of steel chemistry which most strongly influence the final appearance; silicon and phosphorous. Both silicon and phosphorous promote coating growth, and this thicker coating is responsible for the differing appearance.
The amount of silicon added during the steel making process to deoxidize the steel can create differences in appearance of galvanized products. The recommended silicon composition is either less than 0.04% or between 0.15% and 0.25%. Any steels not within these ranges are considered reactive steels and are expected to form zinc coatings that tend to be thicker.
In addition to producing thicker coatings, highly reactive steels tend to have a matte gray or mottled appearance instead of the typical bright coating. This difference in appearance is a result of the rapid zinc-iron intermetallic growth that consumes all of the bright, pure zinc. This growth of the intermetallic layer is generally out of the galvanizer’s control, because they usually do not have prior knowledge of the steel’s composition. However, this increased coating thickness can be beneficial in some respects because time to firrst maintenance is directly proportional to coating thickness.
In _Figure 18_, the micrograph on the left shows a regular zinc-iron alloy, while the micrograph on the right shows an irregular zinc-iron alloy. These clearly show the microscopic level differences that can occur due to the amount of silicon in the steel being hot-dip galvanized.



Figure 18: Regular vs. Irregular Zinc-Iron Alloy Layers The Sandelin curve, as seen in _Figure 19_, compares the zinc coating thickness to the mass percentage of silicon in the steel. The area on the graph labeled “I” is called the Sandelin area and the coatings tend to be thick and dull gray as a direct result of the percentage of silicon present in the base steel. This area is known as the Sandelin range since Dr. Sandelin, a metallurgist, performed the experimental work to show this behavior of galvanized steel. The Sandelin area is roughly between 0.05% and 0.15% silicon. The area on the graph labeled “II”, which represents a steel content of greater than 0.25% silicon, shows the coating thickness increases with increased silicon content and then starts to level off at around 0.4% silicon.



Figure 19: Sandelin Curve



Figure 20: Coating Due to Phosphorous In addition to silicon, the presence of phosphorus influences the reaction between the liquid zinc and the steel, as seen in _Figure 20_. Phosphorus is generally considered an impurity in steel except where its beneficial effects on machinability and resistance to atmospheric corrosion are desired. Some steels such as ASTM A 242 Type 1 present problems because they may contain both a high level of phosphorus and a high level of silicon. The presence of phosphorus generally produces smooth dull coating areas and ridges of a thicker coating where there is increased intermetallic growth. The end-result is a rough surface with ridges appearance.
_Figure 21_ is an example of products with separate galvanized pieces that have
very different appearances due to the difference in steel chemistry. However, all of these products still have an equal amount of corrosion resistance throughout and are acceptable.



Figure 21: Shiny vs. Dull [h=3]Cooling Rate[/h]



Figure 22: Coating Appearance Due to Cooling Rate Difference A visually dull or shiny coating on a product can be caused by the different rate of cooling of a product. In _Figure 22_, the outer edges were cooled rapidly, which allowed free zinc or an eta layer to form on top of the intermetallic layers. The zinc in the center of the product that would have formed the eta layer was consumed in the reaction with the iron after the part was removed from the galvanizing kettle and formed an intermetallic layer that gives the dull gray look. Eventually as the product weathers, the differences in appearance will disappear and it will become a dull gray color throughout.
[h=3]Steel Processing[/h]



Figure 23: Coating Appearance Due to Steel Processing In addition to temperature and chemistry of the steel, the processing of the steel can also create a bright or dull appearance in galvanized products. The top rail in _Figure 23_ has a winding pattern of dull gray areas corresponding to processing during the tube making. The stresses in the steel affect the intermetallic formation and can create this striped look. The corrosion protection is not affected and these parts are acceptable.
​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Finish: Visual Defects[/h]As stated before, the hot-dip galvanized coating could have any number of surface defects. This section will review the various defects and discuss whether or not they are cause for rejection according to the specification. The surface defects reviewed are:
[h=3]A – C[/h]

Bare Spots
Blasting Damage
Chain and Wire Marks
Clogged Holes
Clogged Threads
[h=3]D – E[/h]

Delamination
Distortion
Drainage Spikes
Dross Inclusions
Excess Aluminum in Galvanizing Bath
[h=3]F – O[/h]

Fish Boning
Flaking
Flux Inclusions
Oxide Lines
[h=3]P – R[/h]

Products in Contact
Rough Surface Condition
Runs
Rust Bleeding
[h=3]S – T[/h]

Sand Embedded in Casting
Striations
Steel Surface Condition
Surface Contaminant
Touch Marks
[h=3]U – Z[/h]

Weeping Weld
Welding Blowouts
Welding Spatter
Wet Storage Stain
Zinc Skimmings
Zinc Splatter
​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]A-C[/h][h=3]Bare Spots[/h]



Figure 24: Bare Spots Bare spots, defined as uncoated areas on the steel surface, are the most common surface defect and occur because of inadequate surface preparation, welding slag, sand embedded in castings, excess aluminum in the galvanizing kettle, or lifting aids that prevent the coating from forming in a small area. Only very small areas, less than 1 inch in the narrowest dimension with a total of no more than 0.5%of the accessible surface area, may be renovated using ASTM A 780. This means narrow, bare areas may be repaired; however, if they are greater than one inch-square areas, the product must be regalvanized. In order to avoid bare spots, like those seen in _Figure 24_, the galvanizer must ensure the surfaces are clean and no contaminants are present after pretreatment. If the size of the bare spot or total surface area causes rejection, the parts may be stripped, regalvanized, and then re-inspected for compliance to the standards and specifications.
[h=3]Blasting Damage[/h]



Figure 25: Blasting Damage Blasting damage creates blistered or flaking areas on the surface of the galvanized product. Blasting damage follows abrasive blasting prior to painting of the galvanized steel. It is caused by incorrect blasting procedures creating shattering and delamination of the alloy layers in the zinc coating. Blasting damage, as seen in _Figure 25_, can be avoided when careful attention is paid to preparation of the product for painting. In addition, blast pressure should be greatly reduced according to ASTM D 6386. Since blasting damage is induced by a post-galvanizing process, the galvanizer is not responsible for the damage.
[h=3]Chain and Wire Marks[/h]



Figure 26: Chain and Wire Marks Another type of surface defect occurs when steel is lifted and transported around the galvanizing plant using a chain or wire. These lifting aids can leave uncoated areas on the finished product that will need to be repaired. The superficial marks, like those seen in _Figure 26_, left on the galvanized coating from the lifting attachments are not grounds for rejection as long as marks can be repaired. ASTM specifications do not allow any bare spots on the finished galvanized part.
[h=3]Clogged Holes[/h]



Figure 27: Clogged Holes Clogged holes are holes partially or completely clogged with zinc metal. A good example is the screen shown in _Figure 27_. The zinc was trapped because liquid zinc will not drain easily from holes less than 3/10” (8mm) in diameter due to its high surface tension. Clogged holes can be minimized by making all holes as large as possible. The trapped zinc can be removed by using active fettling when the part is in the galvanizing kettle, vibrating the cranes to jostle the parts, or blowing compressed air onto the galvanized products. This condition is not a cause for rejection, unless it prevents the part from being used for its intended purpose.
[h=3]Clogged Threads[/h]



Figure 28: Clogged Threads Clogged threads are caused by poor drainage of a threaded section after the product is withdrawn from the galvanizing kettle. These clogged threads, as seen in _Figure 28_, can be cleaned by using post-galvanizing cleaning operations such as a centrifuge or by heating them with a torch to about 500 F (260 C) and then brushing them off with a wire brush to remove the excess zinc. Clogged threads must be cleaned before the part can be accepted.
​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]D-E[/h][h=3]Delamination[/h]



Figure 29: Delamination Delamination or peeling creates a rough coating on the steel where the zinc has peeled off. There are a number of causes for zinc peeling. Many large galvanized parts take a long time to cool in the air and form zinc-iron layers after they have been removed from the galvanizing kettle. This continued coating formation leaves behind a void between the top two layers of the galvanized coating. If there are many voids formed, the top layer of zinc can separate from the rest of the coating and peel off the part. If the remaining coating still meets the minimum specification requirements, then the part is still acceptable. If the coating does not meet the minimum specification requirements then the part must be rejected and regalvanized. If delamination, as seen in _Figure 29_, occurs as a result of fabrication after galvanizing, such as blasting before painting, then the galvanizer is not responsible for the defect.
[h=3]Distortion[/h]



Figure 30: Distortion Distortion, as seen in _Figure 30_, is defined as the buckling of a thin, flat steel plate or other flat material such as wire mesh. The cause of this is differential thermal expansion and contraction rates for the thin, flat plate and mesh than the thicker steel of the surrounding frame. In order to avoid distortion, use a thicker plate, ribs, or corrugations to stiffen flat sections or make the entire assembly out of the same thickness steel. Distortion is acceptable, unless distortion changes the part so that it is no longer suitable for its intended use.
[h=3]Drainage Spikes[/h]



Figure 31: Drainage Spikes Drainage spikes or drips are spikes or tear drops of zinc along the bottom edges of the product. These result when the surfaces of the product are processed horizontal to the galvanizing kettle, preventing proper drainage of the zinc from the surface as the product is withdrawn from the kettle. Drainage spikes, as seen in _Figure 31_, are typically removed during the inspection stage by a buffing or grinding process. Drainage spikes or drips are excess zinc and will not affect corrosion protection, but are potentially dangerous for anyone who handles the parts. These defects must be removed before the part can be accepted.
[h=3]Dross Inclusions[/h]



Figure 32: Dross Inclusions Dross inclusions are a distinct zinc-iron intermetallic alloy that becomes entrapped or entrained in the zinc coating. This is caused by picking up zinc-iron particles from the bottom of the kettle. Dross, as seen in _Figure 32_, may be avoided by changing the lifting orientation or redesigning the product to allow for proper drainage. If the dross particles are small and completely covered by zinc metal, they will not affect the corrosion protection and are acceptable. If the dross particles are large, then the dross must be removed and the area repaired.
[h=3]Excess Aluminum in Galvanizing Bath[/h]



Figure 33: Excess Aluminum in Galvanizing Bath Another type of surface defect, shown in _Figure 33_, is caused by an excess amount of aluminum in the galvanizing bath. This creates bare spots and black marks on the surface of the steel. The excess aluminum can be avoided by ensuring proper control of the aluminum level in the galvanizing bath by means of regular sampling and analysis, and by adjusting the levels in a regular and controlled manner. For small areas of bare spots, the part may be repaired as detailed in the specification. If this condition occurs over the entire part, then it must be rejected and regalvanized.
​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]F-O[/h][h=3]Fish Boning[/h]



Figure 34: Fish Boning Fish boning is an irregular pattern over the entire surface of the steel part. This is caused by differences in the surface chemistry of a large diameter steel piece and variations in the reaction rate between the steel and zinc. These reaction differences cause the thickness of the galvanized coating to vary in sharply defined zones across the surface. Fish boning, as seen in _Figure 34_, has no effect on the corrosion protection provided by the zinc coating and is not cause for rejection of the hot-dip galvanized part.
[h=3]Flaking[/h]



Figure 35: Micrograph of Flaking Flaking results when heavy coatings develop in the galvanizing process, usually 12 mils or greater. This generates high stresses at the interface of the steel and the galvanized coating and causes the zinc to become flaky and separate from the surface of the steel. Flaking can be avoided by minimizing the immersion time in the galvanizing kettle and cooling of the galvanized steel parts as quickly as possible. _Figure 35_ shows a micrograph of flaking. In addition, using a different steel grade, if possible, may also help avoid flaking. If the area of flaking is small, it can be repaired and the part can be accepted; however, if the area of flaking is larger than allowed by the specifications, the part must be rejected and regalvanized.
[h=3]Flux Inclusions[/h]



Figure 36: Flux Inclusion Flux inclusion can be created by the failure of the flux to release during the hot-dip galvanizing process. If this occurs, the galvanized coating will not form under this flux spot. If the area is small enough, it must be cleaned and repaired; otherwise, the part must be rejected. Flux spots can increase if the flux is applied using the wet galvanizing method, which is when the flux floats on the zinc bath surface. Flux deposits on the interior of a hollow part, such as a pipe or tube, as seen in _Figure 36_, cannot be repaired, thus the part must be rejected. Any flux spots or deposits,picked up during withdrawal from the galvanizing kettle do not warrant rejection if the underlying coating is not harmed, and the flux is properly removed.
[h=3]Oxide Lines[/h]



Figure 37: Oxide Lines Oxide lines are light colored oxide film lines on the galvanized steel surface. Oxide lines are caused when the product is not removed from the galvanizing kettle at a constant rate. This may be due to the shape of the product or the drainage conditions. Oxide lines, as seen in _Figure 37_, will fade over time as the entire zinc surface oxidizes. They will have no effect on the corrosion performance; only the initial appearance will be affected. This condition is not a cause for rejection of the hot-dip galvanized parts.
​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]P-R[/h][h=3]Products in Contact[/h]



Figure 38: Products in Contact Another type of surface defect is caused by products that come in contact with each other or are stuck together. This usually occurs when many small products are hung on the same fixture, which creates the chance products may become connected or overlapped during the galvanizing process, as seen in _Figure 38_. The galvanizer is responsible for proper handling of all products in order to avoid this defect. In addition, if the surface of a product has a larger bare area than the specified repair requirement allows, then that product must be rejected and regalvanized.
[h=3]Rough Surface Condition[/h]



Figure 39: Rough Surface Condition Rough surface condition or appearance is a uniformly rough coating with a textured appearance over the entire product. The cause for this rough surface condition is hot-rolled steel with a high level of silicon content. This can be avoided by purchasing steel with a silicon content less than 0.03% of the steel by weight. Rough surface condition, as seen in _Figure 39_, can actually have a positive effect on corrosion performance because of the thicker zinc coating produced. One of the few situations where rough coating is cause for rejection is if it occurs on handrails. The corrosion performance of galvanized steel with rough coatings is not affected by the surface roughness.
[h=3]Runs[/h]



Figure 40: Runs Runs are localized thick areas of zinc on the surface. Runs occur when zinc freezes on the surface of the product during removal from the zinc bath. This is more likely to occur on thinner sections with large surface areas that cool quickly. In order to avoid runs, as seen in _Figure 40_, adjustments of the dipping angles can be made, if possible, to alter the drainage pattern to a more acceptable mode. If runs are unavoidable and will interfere with the intended application, they can be buffed. Runs are not cause for rejection.
[h=3]Rust Bleeding[/h]



Figure 41: Rust Bleeding Rust bleeding appears as a brown or red stain that leaks from unsealed joints after the product has been hot-dip galvanized. It is caused by pre-treatment chemicals that penetrate an unsealed joint. During galvanizing of the product, moisture boils off the trapped treatment chemicals leaving anhydrous crystal residues in the joint. Over time, these crystal residues absorb water from the atmosphere and attack the steel on both surfaces of the joint, creating rust that seeps out of the joint. Rust bleeding, as seen in _Figure 41_, can be avoided by seal welding the joint where possible or by leaving a gap greater than 3/32” (2.4mm) wide in order to allow solutions to escape and zinc to penetrate during hot-dip galvanizing. If bleeding occurs, it can be cleaned up by washing the joint after the crystals are hydrolyzed. Bleeding from unsealed joints is not the responsibility of the galvanizers and is not cause for rejection.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]S-T[/h][h=3]Sand Embedded in Casting[/h]



Figure 42: Sand Embedded in Casting Another type of surface defect occurs when sand becomes embedded in the castings and creates rough or bare spots on the surface of the galvanized steel. Sand inclusions are not removed by conventional acid pickling, so abrasive cleaning should be done at the foundry before the products are sent to the galvanizer. This type of defect also leaves bare spots and must be cleaned and repaired or the part must be rejected, stripped, and regalvanized. Sand embedded in a casting can be seen in _Figure 42_.
[h=3]Striations[/h]



Figure 43: Striations Striations are characterized by raised parallel ridges in the galvanized coating, mostly in the longitudinal direction. This can be caused when sections of the steel surface are more highly reactive then the areas around them. These sections are usually associated with segregation of steel impurities, especially phosphorous, created during the rolling process in steel making. Striations, as seen in _Figure 43_, are related to the type of steel galvanized and while the appearance is affected, the performance of the corrosion protection is not. Striations are acceptable on most parts; however, if the striations happen to occur on handrails, then the parts must be rejected and regalvanized. Sometimes regalvanizing does not improve the striations and the handrail must be refabricated out of better quality steel.
[h=3]Surface Contaminant[/h]



Figure 44: Surface Contaminents When surface contaminants create an ungalvanized area where the contaminant was originally applied, a surface defect may occur. This is caused by paint, oil, wax, or lacquer not removed during the pretreatment cleaning steps. Surface contaminants, as seen in _Figure 44_, should be mechanically removed prior to the galvanizing process. If they result in bare areas, then the repair requirements apply and small areas may be repaired, but a large area is grounds for rejection and the entire part must be regalvanized.
[h=3]Touch Marks[/h]



Figure 45: Touch Marks Another type of surface defect is known as touch marks, which are damaged or uncoated areas on the surface of the product. Touch marks are caused by galvanized products resting on each other or by the material handling equipment used during the galvanizing operation. Touch marks, as seen in _Figure 45_, are not cause for rejection if they meet the size criteria for repairable areas. They must be repaired before the part is accepted.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]U-Z[/h][h=3]Weeping Weld[/h]



Figure 46: Weeping Weld Weeping welds stain the zinc surface at the welded connections on the steel. They are caused by entrapped cleaning solutions that penetrate the incomplete weld. In order to avoid weeping welds for small overlapping surfaces, completely seal weld the edges of the overlapping area. For larger overlapping areas, the area cannot be seal welded since the volume expansion of air in the trapped area can cause explosions in the galvanizing kettle. To avoid weeping welds in large overlapping areas, the best plan is to provide a 3/32” (2.4mm) or larger gap between the two pieces when welding them and let the zinc fill the gap between the pieces. This will actually make a stronger joint when the process is complete. Weeping welds, as seen in _Figure 46_, are not the responsibility of the galvanizer and are not cause for rejection.
[h=3]Welding Blowouts[/h]



Figure 47: Welding Blowouts Welding blowout is a bare spot around a weld or overlapping surface hole. These are caused by pre-treatment liquids penetrating the sealed and overlapped areas that boil out during immersion in the liquid zinc. This causes localized surface contamination and prevents the galvanized coating from forming. In order to avoid welding blowouts, as seen in _Figure 47_, check weld areas for complete welds to insure there is no fluid penetration. In addition, products can be preheated prior to immersion into the galvanizing kettle in order to dry out overlap areas as much as possible. Welding blowouts cause bare areas that must be repaired before the part is acceptable.
[h=3]Welding Spatter[/h]



Figure 48: Welding Spatter Welding spatter appears as lumps in the galvanized coating adjacent to weld areas. It is created when welding spatter is left on the surface of the part before it is hot-dip galvanized. In order to avoid welding spatter, welding residues should be removed prior to hot-dip galvanizing. Welding spatter, as seen in _Figure 48_, appears to be covered by the zinc coating, but the coating does not adhere well and can be easily removed. This type of defect can leave an uncoated area or bare spot if the zinc coating is damaged and must be cleaned and properly repaired.
[h=3]Wet Storage Stain[/h]Wet storage stain is a white, powdery surface deposit on freshly galvanized surfaces. It is caused by newly galvanized surfaces being exposed to fresh water, such as rain, dew, or condensation that react with the zinc metal on the surface to form zinc oxide and zinc hydroxide. It is found most often on tightly stacked and bundled items, such as galvanized sheets, plates, angles, bars, and pipes. Wet storage stain can have the appearance of light, medium, or heavy white powder on the galvanized steel product. Each of these appearances can be seen from right to left in _Figure 49_.
One method to avoid wet storage stains is to passivate the product after galvanizing by using a chromate quench solution. Another precaution is to avoid stacking products in poorly ventilated, damp conditions. Light or medium wet storage stain will weather over time in service and is acceptable. In most cases, wet storage stain does not indicate serious degradation of the zinc coating, nor does it necessarily imply any likely reduction in the expected life of the product. However, heavy wet storage stain should be removed mechanically or with appropriate chemical treatments before the galvanized part is put into service. Heavy storage stain must be removed or the part must be rejected and regalvanized.



Figure 49: Wet Storage Stain [h=3]Zinc Skimmings[/h]



Figure 50: Zinc Skimming Inclusions Skimming deposits are usually caused when there is no access to remove the skimmings during the withdrawal of the steel from the galvanizing kettle. The skimmings on the liquid zinc surface are trapped on the zinc coating. In order to remove zinc skimmings without harming the soft zinc coating underneath, lightly brush them off the surface of the galvanized steel during the in-house inspection stage with a nylon-bristle brush. Zinc skimmings, as seen in _Figure 50_, are not grounds for rejection. The zinc coating underneath is not harmed during their removal and it meets the necessary specifications.
[h=3]Zinc Splatter[/h]



Figure 51: Zinc Splatter Zinc splatter is defined as splashes and flakes of zinc that loosely adhere to the galvanized coating surface. Zinc splatter is created when moisture on the surface of the galvanizing kettle causes liquid zinc to “pop” and splash droplets onto the product. These splashes create flakes of zinc loosely adherent to the galvanized surface. Zinc splatter, as seen in _Figure 51_, will not affect the corrosion performance of the zinc coating and is not cause for rejection. The splatter does not need to be cleaned off the zinc coating surface, but can be if a consistent, smooth coating is required.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Additional Tests[/h][h=3]Adherence Test[/h]



Figure 52: Stout Knife Test Testing of the zinc coating adherence to the steel is achieved using a stout knife. The steps used in this test are listed below and a photo of the test being performed can be seen in _Figure 52_. The coating shall be deemed “not adherent” if it flakes off and exposes the base metal in advance of the knifepoint. The test is not an attempt to pare or whittle the zinc coating. If the coating is adherent the knife should put a slight mark in the zinc metal surface, but should not cause any delamination of the coating layers.
*Adhesion Test with a Stout Knife*


Push down point of stout knife
Coating must not flake off exposing the base metal
Do not perform at edges or corners of the product
No paring or whittling with knife is acceptable
[h=3]Bending Test[/h]The hot-dip galvanized coating on a steel bar must withstand bending without flaking or peeling when the bending test is preformed in accordance with the specifications in ASTM A 143. There are various tests used to assess the ductility of steel when subjected to bending. One test may include the determination of the minimum radius or diameter required to make a satisfactory bend. Another test may include the number of repeated bends that the material can withstand without failure when it is bent through a given angle and over a definite radius.
Rebar is commonly bent prior to the hot-dip galvanizing process. Steel reinforcing bars bent cold prior to hot-dip galvanizing should be fabricated to a bend diameter equal to or greater than the specified value in ASTM A 767/A 767M. However, steel reinforcing bars can be bent to diameters tighter than the specified values if they are stress relieved at a temperature of 900 to 1050 F (480 to 560 C) for one hour per inch (25mm) of diameter.
[h=3]Chromating Test[/h]The specification to determine the presence of chromate on zinc surfaces is ASTM B 201. This test involves placing drops of a lead acetate solution on the surface of the product, waiting 5 seconds, and then blotting it gently. If this solution creates a dark deposit or black stain, then there is unpassivated zinc present. A clear result indicates the presence of a chromate passivation coating.
[h=3]Embrittlement Test[/h]When there is suspicion of potential embrittlement of a product, it may be necessary to test a small group of the products to measure the ductility. These tests are usually destructive to the zinc coating and possibly to the product as well. Products suspected of embrittlement shall be tested according to the specification ASTM A 143. Depending on the service conditions the product will be exposed to, one of three embrittlement tests may need to be performed. These embrittlement tests include the similar bend radius test, sharp blow test, and steel angle test. The embrittlement test uses a known force to provide a stress that should be lower than the yield stress of the part. If there is a fracture or permanent damage created during the testing process, the parts must be rejected.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Sampling[/h]A sampling protocol has been developed by ASTM to ensure high quality products because the inspection of the coating thickness for every piece of material galvanized in a project would not be practical. ASTM A123/A123M states for a unit of products whose surface area is equal to or less than 160 in² (1032 cm²), the entire surface of each test product constitutes a specimen. In the case of a product containing more than one material category or steel thickness range, that product will contain more than one specimen. In addition, products with surface areas greater than 160 in² (1032 cm²) are multi-specimen products. There are four important terms used in the ASTM specifications and each is defined below.
[h=3]Sampling Terms[/h]

*Lot* – unit of production or shipment from which a sample is taken for
testing
*Sample* – a collection of individual units of product from a single lot




*Specimen* – the surface of an individual test product or a portion of a
test product which is a member of a lot or a member of a sample representing that lot
*Test Product* – an individual unit of product that is a member of the
sample
For single specimen products, each randomly selected product is a specimen. In thickness measurement tests, five measurements are taken widely dispersed over the surface area of the specimen in order to represent the total coating thickness. The mean value of the five coating thicknesses for one specimen must have a minimum average coating thickness grade of not less than one grade below the minimum average coating thickness for the material category. In _Figure 53_, the separation of a lot into a sample and individual specimen is shown.




Figure 53: Single Specimen Product Sampling A multi-specimen product is defined as having a surface area that may be larger than 160 in² (1032 cm²), have multiple steel thicknesses, or contain more than one coating category. In order to test coating thickness of products whose surface area is greater than 160 in² (1032 cm²), they are subdivided into three continuous local sections with equivalent surface areas, each of which constitutes a unique specimen. In the case of any such local section containing more than one material category or steel thickness range, that section will contain more than one specimen. In _Figure 54_, the separation of a lot into a sample and individual specimen is shown.



Figure 54: Mutli-Specimen Product Sampling For products hot-dip galvanized to either ASTM A123/A123M or A153/A153M, _Table 6_ is used to determine the minimum number of specimens for sampling from a given lot size.

No. of Pieces in LotNo. of Specimens3 or lessAll4 to 5003501 to 120051201 to 320083201 to 10,0001310,001+20*Table 6: Minimum Number of Specimens**for ASTM A123 and A153*
For rebar hot-dip galvanized according to ASTM A767, the information below is used to determine the minimum number of samples per lot, measurements per sample, and the total number of measurements required for each of the different coating thickness measurement techniques.


*Magnetic Thickness:*
3 samples per lot
5 or more measurements per sample
15 measurements, at the minimum, comprise the average

*Microscopy Method:*
5 samples per lot
4 measurements per sample
20 measurements, at minimum, comprise the average

*Stripping and Weighing:*
3 samples per lot

The minimum average coating thickness for a lot is the average of the specimen values and must meet the minimum for the material category. The minimum for an individual specimen is one grade below the minimum for the material category. An individual measurement has no minimum, but bare areas are not allowed on the part. The final inspection of a part shall include thickness measurements and visual inspection. All parts that do not meet the requirement must be resorted and reinspected or rejected and then regalvanized.​


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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Repair[/h]If the galvanized product does not meet all of the requirements of the specification, it must be repaired or rejected along with the lot it represents. When repair of the product is allowed by the specification or bare spots are present, the galvanizer is responsible for the repair unless directed otherwise by the purchaser. The specifications allow for some retesting of products that represent lots or retesting after the lot has been sorted for non-conformance. The coating thickness of the repaired area must match the coating thickness of the surrounding area. However, if zinc-rich paint is used for repair, the coating thickness must be 50% higher than the surrounding area, but not greater than 4.0 mils because mud cracking tends to result when the paint coating is too thick. The maximum sizes for allowable areas that can be repaired during in-plant production are defined in the specifications as summarized below.
[h=3]Maximum Size of Repairable Area[/h]

*ASTM A 123/A 123M:*
One inch or less in narrowest dimension
Total area can be no more than 0.5% of the accessible surface area to be coated or 36 square inches per piece, whichever is less

*ASTM A 153/A 153M:*
The bare spots shall have an area totaling no more than 1% of the total surface area to be coated, excluding threaded areas of the piece

*ASTM A 767/A 767M:*
No area given
If the coating fails to meet the requirement for finish and adherence, the bar may be stripped, regalvanized, and resubmitted
Damage done to the coating due to fabrication or handling shall be repaired with a zinc-rich formulation
Sheared ends shall be coated with a zinc-rich formulation

[h=3]Repair Methods[/h]Any repairs made to galvanized products must follow the requirements of ASTM A 780, which defines the acceptable materials and the required procedures. Repairs are normally completed by the galvanizer before the products are delivered, but under certain circumstances, the purchaser may perform the repairs on their own. The touch-up and repair materials are formulated to deliver an excellent color that matches either brightly coated, newly galvanized products or matte gray, aged galvanized products. Materials used to repair hot-dip galvanized products include zinc-based solder, zinc-rich paint, and zinc spray metallizing, and are explained in the following sections
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Zinc-Based Solder[/h]



Figure 55: Zinc-Based Solder Soldering with zinc-based alloys is achieved by applying zinc alloy in either a stick or powder form. The area being repaired needs to be preheated to approximately 600 F (315 C). The most commonly used solders for repair, as seen in _Figure 55_, include zinc-tin-lead, zinc-cadmium, and zinc-tin-copper alloys.
[h=3]Surface Preparation[/h]According to ASTM A 780, the surface to be reconditioned shall be wire brushed, lightly ground, or mildly blast cleaned. In addition, if wire brushing or light blasting is inadequate, all weld flux and spatter must be removed by mechanical methods. The cleaned area also needs be preheated to 600 F (315 C) and wire brushed while heated. Pre-flux may also be necessary to provide chemical cleaning of the bare spot. Finally, special care should be given to insure that the surrounding galvanized coating is not overheated and burned by the preheating.
[h=3]Application[/h]The soldering method is the most difficult of the three repair methods to complete. A high level of caution must be taken while heating the bare spot to prevent oxidizing the exposed steel or damaging the surrounding galvanized coating. Solders are typically not economically suited for touch-up of large areas because of the time involved in the process and because heating of a large surface area to the same temperature is very difficult. When the repair has been completed, the flux residue needs to be removed by rinsing the surface with water or wiping with a damp cloth.
[h=3]Final Repaired Product[/h]The final coating thickness for this repair shall be agreed upon between the galvanizer and the purchaser, and is generally in the 1 to 2 mil range. The thickness shall be measured by any of the methods in ASTM A 123/A 123M that are non-destructive. Zinc-based solder products closely match the surrounding zinc and blend in well with the existing coating appearance.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Zinc-Rich Paint[/h]



Figure 56: Zinc-Rich Paint Zinc-rich paint is applied to a clean, dry steel surface by either a brush or spray as seen in _Figure 56_, and usually contains an organic binder pre-mix. Zinc-rich paints must contain either between 65% to 69% metallic zinc by weight or greater than 92% metallic zinc by weight in dry film. Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain. Inorganic binders are particularly suitable for paints applied in touch-up applications around and over undamaged hot-dip galvanized areas.
[h=3]Surface Preparation[/h]According to ASTM A 780, the surface to be repaired shall be blast cleaned to SSPC-SP10/NACE No.2 near white metal for immersion applications and SSPC-SP11 near bare metal for less aggressive field conditions. When blasting or power tool cleaning is not practical, hand tools may be used to clean areas to be reconditioned. The blast cleaning must extend into the surrounding, undamaged, galvanized coating.
[h=3]Application[/h]This method of repairing galvanized surfaces must take place as soon as possible after preparation is completed and prior to the development of any visible oxides. The spraying or brushing should be in an application of multiple passes and must follow the paint manufacturer’s specific written instructions. In addition, proper curing of the repaired area must occur before the product is put through the final inspection process. This repair can be done either in the galvanizing plant or on the job site and is the easiest repair method to apply because limited equipment is required. Zinc-rich painting should be avoided if high humidity and/or low temperature conditions exist because adhesion may be adversely affected.
[h=3]Final Repaired Product[/h]The coating thickness for the paint must be 50% higher than the surrounding coating thickness, but not greater than 4.0 mils, and measurements should be taken with either a magnetic, electromagnetic or eddy current gauge. Finally, the surface of the painted coating on the repaired area should be free of lumps, coarse areas, and loose particles.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Zinc Spray Metallizing[/h]



Figure 57: Zinc Spray Metallizing Zinc spray, which is also referred to as metallizing, is done by melting zinc powder or zinc wire in a flame or electric arc and projecting the liquid zinc droplets by air or gas onto the surface to be coated, as seen in _Figure 57_. The zinc used is nominally 99.5% pure or better and the corrosion resistance of the wire or powder is approximately equal.
[h=3]Surface Preparation[/h]According to ASTM A 780, the surface to be reconditioned shall be blast cleaned to SSPC-SP5/NACE No.1 near white metal and must be free of oil, grease, weld flux residue, weld spatter and corrosion products. The blast cleaning must extend into the surrounding, undamaged, galvanized coating.
[h=3]Application[/h]Zinc spraying of the clean, dry surface must be completed by skilled workers and should take place within four hours after preparation or prior to development of visible oxides. Spraying should also be done in horizontal overlapping lines, which yield a uniform thickness more consistent than the crosshatch technique. The zinc coating can be sealed with a thin coating of low viscosity polyurethane, epoxy-phenolic, epoxy, or vinyl resin. The details of the application sequence and procedures can be found in ANSI/AWS C2.18-93. The application of zinc spray can be done either in the galvanizer’s plant or at the job site. In addition, if high humidity conditions exist during spraying, adhesion may be degraded.
[h=3]Final Repaired Product[/h]The renovated area shall have a zinc coating thickness at least as thick as that specified in ASTM A 123/A 123M for the thickness grade required for the appropriate material category. These thickness measurements should be taken with either a magnetic or an electromagnetic gauge for best results. The plain zinc sprays or the sprays with aluminum additives both provide a good match for newly galvanized, bright surfaces. Finally, the surface of the sprayed zinc coating should be free of any lumps, coarse areas, and loose particles.
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## سيد صلاح الصاوى (3 يوليو 2014)

[h=1]Inspection Course[/h]



This course is intended to train individuals on the proper inspection techniques and requirements for hot-dip galvanized steel products. There are four sections in this course:


Hot-Dip Galvanizing Process
Galvanizing Standards
Types of Inspection
Repair
Upon completion of this course, you should be able to recognize specification requirements and perform all inspection steps to ensure conformance with the requirements. Additionally, any inspector who completes the course, and passes the test (80% or better) will receive a printable Certificate of Completion and will be listed on the AGA website as an inspector. _Please make sure to fill out all contact information, *including your country*, in order to accurately be included in the Inspector Listing once the course is successfully passed._
[h=3]Disclaimer[/h]The information contained in this course has been compiled by the American Galvanizers Association (AGA), a not-for-profit trade association whose members represent the after-fabrication hot-dip galvanizing industry throughout the United States, Canada, and Mexico. The AGA makes no endorsement and offers no evaluation of any vendor’s products, whether listed here or not.


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## سيد صلاح الصاوى (7 يوليو 2014)

Welding_and_Hot-Dip_Galvanizing​


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## سيد صلاح الصاوى (16 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سيد صلاح الصاوى (20 يوليو 2014)




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## سعيد01211008493 (18 أكتوبر 2014)

استاذنا سيد صلاح ارجو من حضرتك التكرم والر علي سؤالي ولك جزيل الشكر 
اريد معرفة هل الجلفنه علي الساخن ام علي البارد هي الارخص حيث اني اريد عمل مصنع لجلفنة الاسلاك 
وما هي تكلفة الجلفنه حيث ان السلك المراد جلفنته 1 مللي وقد يصل ال نصف مللي


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