Try CLR.
Small circular stains are dotted on the inside bottom of my stainless steel saucepans after cooking vegetables; there also is a "cloud" on the bottom that is difficult to remove. Should I use a coarse scrubber or chemicals? The saucepans are new.
Try pouring a can of tomatoes into the pan and bring it to a boil. The acid in tomatoes ususally removes any stains from stainless steel. We have enough chemicals in our water treatement plants. . .
yes it is still safe to use. but some of that spots can still be remove just use soap and stealwool if you dont have stealwool use sand paper and soap. if you cant remove them its okay its still safe