Contact corrosion between stainless steel and carbon steel
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Still confused about the reasons for corrosion that occurs when stainless steel comes into contact with carbon steel? If contact between the two causes corrosion, then why can stainless steel and carbon steel be welded? Can it be made into a composite panel?
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The main reason is. Stainless steel and carbon steel form two electrodes, resulting in a galvanic cell reaction that further leads to corrosion
It is mainly due to the contact between the two; firstly, chemical corrosion occurs, as carbon in carbon steel migrates and causes chromium in stainless steel to form chromium carbide, thereby reducing the corrosion resistance of the stainless steel； Second, there is a potential difference between the two, and an electrochemical reaction occurs upon contact. The manufacturing process for stainless steel and carbon steel composite sheets is unique; for example, there is a copper-nickel alloy layer between the two materials, or the combination is achieved only when both materials are physically pure under high vacuum conditions~~
The points made about the fifth and sixth floors are great! Very professional:):):)
The greater the potential difference, the more likely electrochemical corrosion will occur. There is a significant potential difference between carbon steel and stainless steel; therefore, in the same environment, their corrosion rates and degrees are more severe than those of materials made of a single type. Corrosion tends to occur at welds for this reason as well; mainly because there is a potential difference between the welding material and the base material, and pores and depressions at the weld site can accumulate liquid (water or other electrolytes), creating favorable conditions for electrochemical corrosion. The passivation films of the two materials have different properties and stabilities; when they are joined together, the potential difference accelerates the degradation of the passivation films, enhances the depolarization effect, and leads to increased corrosion.
Today I read that austenitic nickel-chromium steel should not come into contact with non-stainless steel metals; so does that mean that when stainless steels with different microstructures come into contact with each other, corrosion may not necessarily occur?
Carbon steel and stainless steel can be welded (careful selection of welding rods is necessary). Moreover, when the two are joined together, carbon steel will rust, mainly due to potential difference corrosion (one material has a higher electron concentration while the other has a lower one... and rusting occurs as a result of the flow of electrons).
Galvanic corrosion is also dependent on the medium in which it occurs