Seminole Metal Finishing offers passivation of stainless steel. Some stainless steels are more corrosion resistant than others, depending on the amount of iron in the base material. 300 series stainless steel contains more chromium and nickel, and is more corrosion resistant, but is not as hard as other stainless steels with a higher content of iron.

Stainless steel is naturally a passive material. However, during the machining and manufacturing process, the stainless is activated by the cutting tools, welding, grinding and drilling processes.

The filings left on the part contain bits of iron which in effect starts the corrosion process on the surface of the material. Passivation improves the materials’ corrosion resistance by removing iron and other undesirable foreign materials from the surface of the stainless steel and leaves a passive film on the surface of the metal. Passivation usually does not change the appearance of the base material.

The specifications for different types of passivation are ASTM-A-380 and ASTM-A-967. QQ-P-35 has been cancelled and replaced with ASTM-A-967.