passivation is normally done in a chemical tank process. The process involves smoothing the surface, eating away at any crevices in the grain boundaries making it more like a "weathered rolling hills" instead of "sharp craggy mountains". the smoother surface keeps the exposed areas from being affected by salt water
etc. Most stanchions, pulpits etc are "electro polished" which is pretty much the same effect.:>)
Stainless steels are corrosion-resistant by nature, which might suggest that passivating them would be unnecessary. However, stainless steels are not completely impervious to rusting. One common mode of corrosion in corrosion-resistant steels is when small spots on the surface begin to rust because grain boundaries or embedded bits of foreign matter (such as grinding swarf) allow water molecules to oxidize some of the iron in those spots despite the alloying chromium. This is called rouging. Some grades of stainless steel are especially resistant to rouging; parts made from them may therefore forgo any passivation step, depending on engineering decisions.
A typical passivation process of cleaning stainless steel tanks involves cleaning with sodium hydroxide and citric acid followed by nitric acid (up to 20% at 120 °F) and a complete water rinse. This process will restore the film, remove metal particles, dirt, and welding-generated compounds (e.g. oxides).
One aircraft manufacturer's corporate standard for passivation of stainless steel parts involves coating or submerging them in nitric acid solution for 40 to 60 minutes, then wiping them with water-soaked cloth.