Passivation
Passivation is the treatment of stainless steel in a nitric acid or citric acid solution to remove iron contamination on the surface. The contamination is from fabrication such as stamping, drilling, machining, welding, cutting, forming or wire brushing.
Passivation does not change the appearance of the stainless. If the stainless has been heat treated or welded, the resultant scale or discoloration must be removed by either abrasive methods or by pickling. The processor must know the alloy of stainless steel before passivation is attempted so that the proper solution will be used.
Salt spray or humidity testing as well as copper sulfate testing accomplish testing to verify the effectiveness of the passivation treatment.
Passivation is processed to meet ASTM B-912, ASTM A-967 and ASTM A-380 specifications, which supercede the previous Government Specification of QQ-P-35.