Stainless Steel is a type of corrosion resistant steel that does not corrode when exposed to wet conditions. On the other hand carbon steel rusts when exposed to air and moisture. Resulting in a porous and fragile iron oxide surface layer.
Stainless Steel like corrosion resistant steels contain alloying elements that protect them from corrosion. Stainless steel contains chromium, which causes it to undergo passivation and form a film of chromium oxide. This passivation techniques prevents the steel from corroding further. Corrosion resistance of steels varies. The alloying elements make steel resistant to specific types of corrosive elements. The increase in chromium and molybdenum content of Stainless Steel makes it resistant to reducing acids like hydrochloric and dilute sulphuric acids. Localized corrosion involves pitting corrosion, crevice corrosion and stress corrosion cracking. Pitting corrosion leads to small holes in the metal. Crevice corrosion happens where the working fluid has limited space, mostly in confined spaces. And stress corrosion is the formation of crack in the steel when exposed to a corrosive environment. Increasing the chromium, molybdenum and nitrogen content allows to resist these localized corrosion.