Passivation is the removal of free iron or steel compounds from the surface of stainless steel by means of a chemical solution, most typically by a treatment with a nitric acid solution that will remove the surface contamination but will not significantly affect the stainless steel itself. A mild oxidant, such as a nitric acid solution, enhances the spontaneous formation of the protective, passive film. In layman's terms, the passivation process removes “free iron” contamination left behind on the surface of the stainless steel as a result of machining and fabricating processes. These contaminants are potential corrosion sites which, if not removed, result in premature corrosion and ultimately result in deterioration of the component.

Common Specifications include: QQ-P-35 Type II and VI; ASTM-A-967 Nitric 1 and 2; ASTM-A-380 Code G and F