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Salt spray test Corrosion principle
Feb 26, 2018

Salt spray corrosion of metal materials, mainly conductive salt solution into the metal electrochemical reaction occurs within the formation of "low potential metal - electrolyte solution - high potential impurity" micro-battery system, the occurrence of electron transfer, as the anode metal dissolved, The formation of new compounds that corrosives. The same applies to the metal protective layer and the organic material protective layer. When the salt solution as the electrolyte penetrates into the interior, a micro cell having the metal as the electrode and the metal protective layer or the organic material as the other electrode is formed.

 

Salt spray corrosion damage process plays a major role in the chloride ion. It has a strong penetration ability, easy to penetrate the metal oxide into the metal, destroy the passive state of the metal. At the same time, chloride ion has a small hydration energy, easily adsorbed on the metal surface, instead of protecting the metal oxide layer of oxygen, the metal is damaged.

 

In addition to chloride ions, the salt spray corrosion mechanism is also affected by the oxygen dissolved in the salt solution (which is essentially a salt film dissolved on the sample surface). Oxygen can cause the depolarization of the metal surface and accelerate the dissolution of the anode metal. Due to continuous spray during the salt spray test, the salt solution on the surface of the sample is continuously deposited so that the oxygen content remains close to saturation. The formation of corrosion products expands the volume of salt solution infiltrated into the metal defects, thereby increasing the internal stress of the metal, causing stress corrosion and causing the protective layer to bulge.


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    Email: hyh5@china-hyh.com


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