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Stainless passivation is the process by which stainless steel will spontaneously form a chemically inactive surface when exposed to air or other oxygen-containing environments. Some important facts to know when considering passivating stainless steel:
This last step is necessary because during handling and processing such as rolling, forming, machining, pressing, tumbling, and lapping, particles of iron or tool steel or abrasive particles may be embedded in or smeared on or into the surfaces of stainless steel components. If allowed to remain, these particles may corrode and produce rust spots on the stainless steel. This is due to the formation of a galvanic couple between two dissimilar metals that can promote a corrosive reaction. To dissolve the embedded or smeared iron and prevent this condition, as well as restore the original corrosion-resistant surface, semi-finished or finished parts are given a ‘passivation’ treatment.
The passivation of stainless steel is performed when free iron, oxide scale, rust, iron particles, metal chips or other nonvolatile deposits might adversely affect the metallurgical or sanitary condition or stability of the surface, the mechanical operation of a part, component or system, or contaminate the process fluid. Stainless steel is passivated through a cleaning cycle to remove oils, grease, compounds, lubricants, and residue followed by a nitric or a citric acid bath or a by an oxidant that removes free iron and contaminates.
Passivation is performed on clean stainless steel, providing the surface has been thoroughly cleaned or descaled. Since the term “passivation” is used to describe distinctly different operations or processes relating to stainless steels, it is necessary to define precisely what is meant by passivation.
Electrolurgy is an industry leader in passivation services, delivering the highest quality passivated products to our customers since 1969. Here at Electrolurgy, we offer stainless steel passivation services with a focus on ASTM A967, ASTM A380, ASTM B912, and QQ-P-35C specifications. Call or contact us today to speak to a Electrolurgy specialist about stainless steel passivating.