# انواع ال Corrosion



## Eng-Maher (23 مارس 2010)

Types of Corrosion​ 


Corrosion can be categorized in some common types
uniform corrosion
pitting corrosion
galvanic corrosion
crevice corrosion
concentration cell corrosion
graphitic corrosion

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Uniform or General Corrosion
The metal loss is uniform from the surface.
Often combined with high-velocity fluid erosion, with or without abrasives.
Pitting Corrosion
The metal loss is randomly located on the metal surface.
Often combined with stagnant fluid or in areas with low fluid velocity.
Galvanic Corrosion
Occurs when two metals with different electrode potential is connected in a corrosive electrolytic environment.
The anodic metal develops deep pits and groves in the surface.
Crevice Corrosion
Occurs at places with gaskets, bolts and lap joints where crevice exists.
Crevice corrosion creates pits similar to pitting corrosion.
Concentration Cell Corrosion
Occurs where the surface is exposed to an electrolytic environment where the concentration of the corrosive fluid or the dissolved oxygen varies.
Often combined with stagnant fluid or in areas with low fluid velocity.
Graphitic Corrosion
Cast iron loosing iron in salt water or acids.
Leaves the graphite in place, resulting in a soft weak metal.​


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## Eng-Maher (23 مارس 2010)

Electrode Potential and Galvanic Corrosion

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he potential difference between an anode and a cathode can be measured by a voltage measuring device. The absolute potential of the anode and cathode cannot be measured directly. Defining a standard electrode, all other potential measurements can be made against this standard electrode. If the standard electrode potential is set to zero, the potential difference measured can be considered as the absolute potential.
Standard Hydrogen Electrode
The half-cell in which the hydrogen reaction takes place is called the Standard Hydrogen Electrode - SHE
Standard Electrode Potential
The potential difference measured between metal M, and the Standard Hydrogen Electrode - SHE
The electrochemical series consists of a list of metals which have been arranged in order of their standard electrode potentials.








IMPORTANT! Metals which are higher in the electrochemical series displace metals which are lower in the sequence, which means when connecting two metals, the metal with lowest potential will corrode.
Corrosion Problems Connecting Copper and Iron/Steel
A very common connection in piping systems is copper and iron/steel. In a connection like this iron/steel will corrode many times faster than iron/steel alone.


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## سامي الابراهيمي (4 ديسمبر 2010)

مفيد جدا


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## Eng-Maher (18 نوفمبر 2011)

شكرا اخى الفاضل


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## saif ghannai (13 ديسمبر 2011)

thanks a lot


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## faisal hemali (3 فبراير 2012)

يسلمو على الموضوع


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## Eng-Maher (15 سبتمبر 2013)

يرفع للافادة


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## al-senator (17 سبتمبر 2013)

شكراً لك وجزاك الله كُل خير


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