Re: Por-15 - Silver??
Are you talking about gas tank sealer? (POR-15 has a whole catalog full of different products) If so, yes, I've used it, and it worked great. I cleaned the tank inside and out and got rid of as much external rust as I could with a wire wheel. Then I used a small brush to dab the pinholes with sealer from the outside. After that dried, I did the inside of the tank as directed. After that, you end up with half a quart that you've emptied into a pan that they say you can't reuse(contact with air hardens it). So I painted the outside of the tank with it. After 3 years, it's only bubbled in a couple of spots where stones chipped it, and doesn't leak a drop. Good stuff.
Pete