# Iron(II) oxide on stainless steel?

I noticed after some use that a stainless steel spoon that I have started forming $\ce{FeO}$. Stainless steel is not supposed to rust like this. I don't know of any black iron hydroxides, chromium oxides, or chromium hydroxides so that lead me to deduce that it is Iron(II) Oxide.

But why would stainless steel oxidize? I mean it does not make any sense since I was told that stainless steel does not oxidize.

And how can I get rid of the oxide? Putting the spoon in phosphoric acid perhaps since phosphoric acid is a really good rust remover?

• But the spoon is only weakly magnetic and it has this black oxide. It even says "Stainless steel". Water must have done this because it wasn't there before and now it is and it never happened from exposure to the air. And if the chromium oxidized I would see a green oxide on my spoon instead of black. I know it can't be from carbon because it would form carbon dioxide. I don't know of any black nickel oxides and nickel isn't likely to oxidize in the first place. So it has to be the iron that oxidized. – Caters Sep 3 '15 at 21:02
• I'd really like to see a photo before drawing any conclusions. – Ivan Neretin Sep 3 '15 at 21:14