WTF, steel, I thought you were supposed to be stainless

November 21, 2012 12:02 PM

I discolored a stainless steel pot lid. What can I do about it?

So, I am an idiot who left the stove on, heating up an empty cast-iron pan and the stainless steel lid that was on it.

It was really hot for a pretty long time.

Now the underside of the lid is discolored a burnt coppery color, and all the Barkeeper's Friend in the world isn't doing the job of getting this nice lid back to silver.

What else can I try?

posted by entropone to home & garden (10 answers total)

You have changed the temper of the steel, you could try to heat-treat it and retemper it by heating it up and then letting it cool down very slowly.

Heat it up to glowing hot and then stick it into a very hot oven. Then turn off the oven and let the lid and oven cool down together slowly.
posted by The 10th Regiment of Foot at 12:07 PM on November 21, 2012

It's called stainless steel only because it stains "less" than regular steel.
posted by rhizome at 12:10 PM on November 21, 2012

Try a high quality copper scrubbing pad. Like steel wool only copper.
posted by neversummer at 12:15 PM on November 21, 2012

10th Regiment has the right idea, but rhizome and neversummer are a bit off the mark. The "stainless" in "stainless steel" refers to corrosion resistance, and your pot lid has not corroded. Nor is it coated with a layer of discoloration that could be scrubbed off.

You have indeed changed the temper of the steel on the lid, which has changed its physical properties, including its reflectivity which is why it now looks coppery. There is probably nothing that you can do -- you could try 10th Regiment's suggestion of re-tempering the steel, but I doubt that you can do this at home in a sufficiently-controlled fashion to be able to restore the lid to its original temper. I would expect that all you would manage to do would be to worsen the discoloration that has already happened, perhaps rendering the entire pot lid a sort of mottled blue-black and brown and making it brittle in the bargain.

Fortunately there is really nothing wrong with the lid. You now have a cosmetic defect on the underside of the lid (where you can't even see it during use). It is probably not functionally impaired in the least, and will do its job just fine. What I would do in your situation is I would just completely ignore the problem because it isn't really a problem at all. The lid will work perfectly well, and nobody in the world except you is going to care that the underside of that lid is brownish, so if you can stop caring about it yourself then the problem is solved.
posted by Scientist at 12:27 PM on November 21, 2012 [7 favorites]

My experience with exactly the same kind of phenomenon is that the discoloration goes pretty much all through and isn't scrubbable awayable. So if T10thRoF's method doesn't work, this is what you'll end up with...

[In my view, this type of wear marks record the surface of the life I've lived. The most blatant example from my kitchen is a chip of a few millimeters that I stupidly broke out of a very nice and expensive Japanese vegetable cutting knife by trying to chop through something frozen. That was when I was 23; I was mad at myself for weeks. I'm now 53, and have managed to almost entirely hone away that gap, which sort of makes me sad now.

You could view it as a thing of value.]
posted by Namlit at 12:39 PM on November 21, 2012 [7 favorites]

Get a metal polish and it will be as good as new. You may have to go at it with jewelers rouge.
posted by wongcorgi at 1:18 PM on November 21, 2012

The colors of tempering are interference film colors which depend on the thickness of an oxide layer.

As wongcorgi says, they are easily removed with an abrasive.

I suggest going to an auto parts store and getting a few sheets of wet/dry 600 grit sand paper-- 1200 grit if you want a mirror finish.
posted by jamjam at 1:36 PM on November 21, 2012 [2 favorites]

I also agree that it is probably a layer of oxide rather than an actual discoloration of the metal. Because if it was a discoloration all the way through, the outside of the lid would also be the same color.

Try CLR, or Lime Away, or toilet bowl cleaner with muriatic acid (HCL) in it. Do not mix them; and apply them for only brief periods so you don't discolor anything else.

You can also try a green Scotchbrite pad if those don't work. They will mar the finish, so decide first whether you want a dull finish inside the lid, or the staining.
posted by gjc at 5:05 PM on November 21, 2012 [1 favorite]

Just as an FYI - stainless steels, for the most part, are like normal (low carbon) mild steel in that they do not take a temper. When tempering a piece of steel by running the colors (quenching when the blade edge is the color associated with the hardness you want) it's important to know what kind of steel you're dealing with as the resulting hardness associated with a given color will vary from alloy to alloy.

TLDR version - you don't need to do anything about this other than scrub off the discoloration, and you don't even need to do that.
posted by Kid Charlemagne at 12:46 AM on November 22, 2012

Yeah, this is an oxide layer on the surface, and does not go all the way through. The problem with trying to remove it is that it's a *tough* oxide layer, and any abrasive hard enough to cut through it is also going to scratch up the underlying steel. If the lid was highly polished /mirror-like, you're not going to be able to reproduce that surface without special equipment. If it was a "brushed" finish, you might be able to imitate it with hardware store stuff, but it will still be nigh impossible to get it looking like it did originally. Basically this boils down to, which cosmetic defect would you rather live with?
posted by jon1270 at 6:58 AM on November 22, 2012