Which specification specify an unacceptable oxidation color and visual inspection of stainless steel after welding? This photo recieved from our client’s comments
stainless steel has a very thin and stable oxide film rich in chrome. This film reforms rapidly by reaction with the atmosphere if damaged. If stainless steel is not adequately protected from the atmosphere during welding or is subject to very heavy grinding operations, a very thick oxide layer will form. This thick oxide layer, distinguished by its blue tint, will have a chrome depleted layer under it, which will impair corrosion resistance. Both the oxide film and depleted layer must be removed, either mechanically, or chemically (acid pickle with a mixture of nitric and hydrofluoric acid).
For small bore pipes I don’t think picking and passivation inside the pipe is not an easy process and I am not quite sure it is possible,
on outside yes of course we can pickle and passivate.