My neighbor threw out this pan. She scoured it. But she couldn't remove the discoloration and blackness which, she worried, indicates chemical changes and carcinogens. She said I could have it, if I want. I took it home, but can't scrub away the brown and black colors either. Is she correct? What's wrong with this pan? Can I salvage this pan? Can I safely cook with this pan? The first picture is the bottom of the pan. The rest of pics are the top.
If any of it is burnt-on crud, rather than just oxides, bagging the pan in a plastic bag with ammonia (does not need to be full of ammonia - just a bit to make fumes that the bag holds) for a few days might help it come off. Not a health/safety concern, but it's a good trick for burnt-on grease type stains and can improve appearance considerably.
I'd guess the black crud that has been scraped through on the outside bottom would probably be removed with scrubbing after ammonia treatment, and the yellow/tan discoloration is more likely oxides. Likewise the narrow ring of black crud inside the pan.