Steel is an alloy of iron and other materials,especially carbon. The corrosion-resistant properties of steel are related somehow to the chemical relationship between the various elements in the alloy. Probably the carbon oxidizes the iron so that oxygen has less of a time getting at it, but chemically it should still be possible to rust it because oxygen is far better at oxidizing metals than carbon is.

At a guess, it somehow raises the energy threshold required to do corrosion in the first place, so that stainless steel will not corrode except under very high temperatures, in which it surely will.