This question on Quora makes me think people don’t really understand the nature of stainless steel.
We get this exact question quite frequently.
The chromium in stainless steel is not the same as the kind features in the movie Erin Brokovitch. It is a safe form that is actually an essential mineral that the body needs in trace amounts.
When you overheat stainless steel, it doesn’t release chromium, it actually promotes the formation of more chromium oxide, which is the whole purpose of the chromium in stainless steel. Chromium oxide is a clear layer that coats the top of the stainless steel surface and prevents the iron from rusting. When you overheat, you form more of it which can cause the rainbow shimmer (often referred to as heat tint) you sometimes see on the surface of stainless steel; this is uneven thicknesses of the clear chromium oxide refracting the light differently where the layers differ in thickness, thus altering the angle of refraction of the colors of white light. Here is what heat tint looks like:
You can fix heat tint by using a fine polish like Bar Keepers Friend.
You may not realize this but the daily use of stainless steel constantly damages the chromium oxide finish. But chromium is highly attracted to the oxygen in the air and will bond with it, which means your stainless steel cookware will always self-repair after damage. It wouldn’t if you were in an oxygen free environment, like the moon, but then rust needs oxygen to form a well so it wouldn’t matter. I don’t know why I thought of that. 🙂
Overheating can cause other problems. The inside of stainless steel cookware often gets lots of pits from the use of metal kitchen tools and acidic foods, like tomato sauce. Hard water deposits can collect in these pits and will get charred and turn black when you severely overheat a dry pan. You can read more about that here.
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