I don't know much about that stuff, but if it is some kind of metal cleaner, I'm sure it has some kind of compound in it that is abrasive? Maybe that's wrecking it, I wouldn't use that on anything but stainless....
You hear people talking alot about it. Its a mild clenaser. It contains an acid compound..It probalby works on Stainless and other metals, it might even work on a Kettle with some good results. Never heard of it staining a Kettle.. Lets see it and we can go from there.
So i am cleaning my 7os patent black metal handle and i was using barkeepers friend but now there is a haze where i put barkeepers friend that wont come off