Stainless steel does not “rust” as you think of regular steel rusting with a red oxide on the surface that flakes off. Corrosion is generally caused by contaminants settling on the surface of the stainless steel.

For example, stainless steel and aluminium metals will react when wet, creating a red oxide, especially when salt is present. The metal with the lower oxidation potential will corrode; in this case, the aluminium.