well dont know what i did wrong but one tank finally started cracking and chipping away inside, that was after 3 days of drying and then i put gas in it. the other im still letting dry, which it should already be dry. ive used it on the outside of a gas tank with minor pin holes and it worked great but in thinking now its going to do the same thing in my other tank, chip and crack. oh well i guess ill be buying a new tank.