I have used PC 7 epoxy. This is right out of the "old" space age and bullet proof. (look up the product). Then painted over with exterior gas tank paint https://www.rust.co.uk/product...guard-epoxy-coating/ This small repair was. done on a TVR stainless steel fuel tank and will outlast the tank and car. The repair area was well sanded and degreased many times. I believe that this is much better than the inside tank sealers that also handle small pin hole leaks but rely on getting the inside vey clean which is very hard to do correctly.
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