for instance Cr-Ni steeldoes this refer to plated steel or a uniform mixture
stainless steel is an alloy normally iron with additions of C, Mn, Ni, Cr, and Nb - amounts added depend on properties required. Corrosion resistance is due to a very thin but dense layer of chromium oxide which forms at the surface and prevents further attack. Ordinary steel on the other hand becomes coated with a porous layer of iron oxide(rust) through which the atmosphere can pass and cause further corrosion.
