Passivation issues of 316L stainless steel pipes
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I have a question for the experts: For 316L pipes, the following three types of passivation films are formed – through pickling and passivation, through bright annealing, and through electrochemical polishing. What are the differences between these three types of passivation films? I seek advice from experts
It depends on where it will be used. In our factory’s process for producing stainless steel pipes, acid washing, passivation, and bright annealing are the most common methods. In the instrumentation industry, bright annealing is preferred, as it involves gas-shielded annealing as well, which prevents the formation of an oxide layer on the surface; under vacuum conditions, the material remains in better condition. The other two are probably not as good as those that have been annealed in a low-light environment.
There is an article that explains this in great detail; it states that differences in the chromium-iron ratio and chromium-nickel ratio within the passivation layer lead to vastly different corrosion resistance. I’ll look for it specifically and send it once I find it