Can pickling and passivation cause stainless steel to thin?
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We have a stainless steel 304 device equipped with expansion joints that are 3 mm thick. The surface of these joints looks very unsightly after manufacturing. We would like to carry out acid washing and passivation, but the technicians say that the thickness is too low; they are worried that acid washing and passivation will cause the thickness to decrease too much, resulting in it not meeting the requirements, and therefore they won’t allow us to do this process Can pickling and passivation cause stainless steel to thin? How much can the thickness be reduced?
The pickling of stainless steel is merely used to remove substances such as grease and rust; passivation involves forming a passive film on the surface of the stainless steel. If the chemical formula used in this process isn’t highly corrosive, it will not cause the metal to thin out.
I agree with the person above; if the ratio of ingredients in the stainless steel pickling and passivation solution is correct and the processing time is properly controlled, there will be no problems.
This post was last edited by zhangjuhua on 2015-6-9 22:19. I’m not sure what to use for cleaning; if it contains salt or acid, it can damage the passivation layer
The person who asked this question does not understand the mechanism of acid cleaning and passivation. The purpose of acid cleaning is mainly to remove surface oils, rust, paint, welding slag, etc., in order to prepare for passivation. Passivation aims to create a very thin, dense passivation film that gives stainless steel corrosion resistance. It must be said that there is some truth to his concerns; pickling does cause a certain degree of thinning, but this amount of thinning is necessary for the pickling and passivation process. The thinning mainly occurs in the chromium-deficient areas on the surface, by just 0.01 mm. Once these chromium-deficient areas are removed, chromium-rich areas are formed on the surface, which enhances its corrosion resistance.
Search for \"pickling paste\" on Baidu directly. . .
It is generally done using passivation paste, and it basically has no effect on the thickness.
@Austenitic stainless steel has been explained quite clearly. In fact, acidic media do not cause corrosion to austenitic stainless steel; as long as the formulation of the pickling paste is appropriate – with acidity not being too high, the pickling temperature not being too high, and the pickling time not being too long – corrosion within 2 um can generally be prevented.
Austenitic stainless steel must not be used with salts or acids. Pickling and passivation will definitely cause thinning, but compared to the corrosion-induced thinning resulting from reduced corrosion resistance after passivation, this is acceptable and negligible.
The thinning caused by pickling is offset by the thickening resulting from passivation. It can be considered without thinning