Must stainless steel equipment be pickled and passivated after manufacturing?
Thread Content
As the title suggests, is it necessary to acid wash and passivate stainless steel equipment after it has been manufactured? Is there any basis for this? Some drawings explicitly state the need for pickling and passivation, while some design drawings for stainless steel equipment do not mention it – should we then refrain from carrying out such processes?
The last edit to this post was made by gn_1984 on 2018-8-9 at 15:00. HG/T20584-2011 requires that the surfaces of stainless steel in contact with corrosive media be subjected to acid washing and passivation; similarly, the surfaces of stainless steel components after heat treatment also need to undergo acid washing and passivation. Therefore, it’s not necessary to perform acid washing and passivation on all stainless steel materials, nor on all of their surfaces – only those surfaces that are in contact with corrosive media. However, some people carry out acid washing and passivation on the outer surface for aesthetic reasons; this is too costly for large stainless steel equipment. Small devices are okay too.
If in contact with corrosive materials, passivation is certainly required to ensure corrosion resistance. If the medium is not subject to corrosion, it is acceptable not to passivate it for reasons such as maintaining material cleanliness; however, passivation gives a better appearance and removes some of the contaminants that arise during processing, so obviously passivation is preferable. So, passivation is generally also required.
Not necessarily; it depends on the customer’s requirements. Some require polishing, while others require pickling
If the contract does not specify any particular requirements, acid washing and passivation are generally carried out; even if the medium is not corrosive, there is still contamination during the manufacturing process, and acid washing and passivation are used to improve the aesthetic appearance.
Mm-hmm, thank you. In the past, stainless steel equipment has always been pickled and passivated. Suddenly, a newcomer asked me if there was any basis for it, since neither the contract nor the agreements nor the drawings specified anything. I also remember where I saw the source, but then suddenly can’t recall where it is, so I came to ask the question here on this forum. :)
I’ve encountered situations where both polishing and pickling/passivation were required, which seemed contradictory, but I still followed the drawings. They at the design institute themselves don’t know either: L
Last year we encountered a big problem: the contract workers didn’t notice that the stainless steel equipment required acid washing both on the inside and outside. After the work was completed, the supervisor insisted that the inside also be acid washed, but the workers were unwilling to do it.
Haha, I’ve encountered situations where both pickling and polishing were required too; P;P
To determine the source, clause 7.8 of HG/T2806-2009 \"Detailed Rules for the Manufacturing Management of Austenitic Stainless Steel Pressure Vessels\" stipulates that pressure vessels or pressure-bearing components made of stainless steel or composite stainless steel that require corrosion resistance must be pickled and passivated.
Acid washing is required after mechanical polishing, while it is not necessary after electrochemical polishing.