Why stainless steel.won’t Corrode?

Stainless steels resist corrosion because they have a self-repairing “passive” oxide film on the surface. As long as there is sufficient oxygen to maintain this film and provided that the level of corrosives is below the steel’s capacity of the particular material to repair itself, no corrosion occurs. If there is too high a level of (say) chlorides, pitting occurs. As an example, 316 works well in tap water (<250ppm), but will rapidly corrode in seawater because seawater has very high chloride levels (20,000ppm).

Disclaimer: As obtained from the Internet