Like the others said, Kreem does not simply cover up rust. The first step will get the rust out of your tank. Don't get in a hurry, let it sit with the solution in the tank at least 24 hrs. Pour it out in a bucket, if the tank is still rusty you can pour the solution back in and do it again. Done properly, Kreem will seal pinhole leaks and ensure that you will not have a rust problem reoccur. I have used it several times on old bikes, most notably on a DT 175 that was so rusty, light passed through the pinholes. It is good as new now, two years later.