If it's mandatory is usually determined by your project specification, thus most often decided by your client. Design codes wont specify such things as they deal with other things, so dont look in there forthese details. If it's good (industry) practice or not is something different.
Which of the 2 was your original question really about? What's your own idea?
/edt; please dont double post, it's against forum policy. I have red flagged your other thread for deletion by the mods.
It is required if you are trying to optimize corrosion resistance.
Remember, passivation in SS is a cleaning operation, it uses an acid to remove residuals that can degraded corrosion performance.
Thanks a lot for the response, Pickling and passivation is not required by our project specification. Since we have got some of the DSS joints rusted after welding so we decided to clean those. My question, is it enough to clean those joints through pickling only or we shall have passivation as well to those joints. If we do not do passivation will it accelerate the corrosion rate of those joints due to pickling?
Let's assume that the rust is just from surface oxidation and that you C and A:F numbers are all good.
If you used a pickling paste (such as RedOne) and then washed and either neutralized or at least checked pH to assure no residual acid, then you are OK.
How rough did they get when you pickled? If they got very rough and porous looking then you have some serious weld issues.
It sounds that the original DSS material wasn't cleaned thoroughly after fabricated, so it rusted at some of the weld joints. The pickling process can remove the rust material as well as other particles from the metal surface. After then, the passivation can produce a passive film effectively and quickly to protect the material from corrosion.
IMO, if the DSS system is critical to the process, the passivation treatment is recommended.
