The contact problem between stainless steel and carbon steel
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When installing pipes, stainless steel pipes are generally required to be kept away from direct contact with carbon steel. Current standards specify that between stainless steel, nickel, and nickel alloy pipe components and carbon steel pipe supports, a stainless steel gasket or a non-metallic gasket with a chloride content of no more than 50 ppm should be used as a spacer. Will the stainless steel gasket here not corrode over time after coming into contact with the carbon steel pipe supports and hangers? Can someone explain this?
The bracket isn’t directly connected to the pipe
I mean, once the stainless steel plate is corroded, won’t the pipe be in direct contact with carbon steel?
Oh, I see what you mean! But don’t you paint your stainless steel pipes? Painting can prevent this problem
By the time you’ve corroded the stainless steel plate, it will be time to replace this entire set of equipment as well……
Thank you all for your feedback! My understanding is that during installation, contact between carbon steel and stainless steel should be avoided as much as possible; in practice, corrosion-related failures due to contact between stainless steel and carbon steel must have occurred as well. Isn’t the corrosion mechanism when the stainless steel plate comes into contact with carbon steel supports and hangers the same as that in pipes? Additionally, the standard does not specify what thickness of stainless steel plate should be used; determining the appropriate thickness is also a problem!
Regarding the issue of contact between stainless steel and carbon steel, the main goal is to prevent galvanic corrosion; carburization cannot occur either, as there is no physical pathway for elements to penetrate into one another (or to diffuse) between solid metal structures, and this is not feasible either from a thermodynamic perspective. As for galvanic corrosion, different metal materials have varying natural potentials; when this difference reaches a certain level, and if an electrolyte is present externally, electron transfer occurs between the different metals, which results in the flow of electricity. This electron transfer leads to the corrosion of the metals. As for which type of metal material is prone to corrosion, it depends on the electrochemical potential sequence of the metal, that is, its natural potential level. For example, between copper and zinc, zinc has a lower natural potential than copper, so zinc corrodes. Common dry batteries utilize this principle, but graphite is used in place of copper. There is a significant potential difference between stainless steel and carbon steel. If they come into contact with each other in the presence of water or other conductive substances, corrosion will occur. Under normal conditions, it is carbon steel that corrodes; however, in an environment containing chloride ions such as seawater, carbon steel suffers only mild corrosion, while stainless steel experiences pitting corrosion. This is because the protective oxide layer on the surface of stainless steel is quickly damaged by the highly penetrating chloride ions, leading to localized electrochemical corrosion, whereas carbon steel does not suffer from pitting corrosion.