How to remove rust stains from bathtub?

I have for the first time a self-cleaning oven, but instructions said I can't leave the racks in oven while it is cleaning....is this true???? really???? Anyway, I took racks out and soaked them in tub with some "Dawn". After I scrubbed them down, and rinsed them, I noticed rust spots in the tub. The tub is original tub, house built in 1954, so I am thinking "porcelain?" not sure what tubs were made of back in the day. Can this be removed?

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