Originally posted by Big Tracks
A couple of years ago I bought a '79 Yamaha two-wheeler that had been parked in a guy's shop for over twenty years. He parked it with half a tank of gas in it.

Needless to say, the tank was a rusted, caked up disaster. A friend of mine who restores bikes told me to go to a motorcycle shop and get a kit (and I've forgotten the name of the stuff) to fix that very problem. Surely they make a kit for cars, too.

The kit contained a bottle of acid (and I've also forgotten what kind of acid) that will dissolve the rust and a two-part creamy looking liquid treatment to completely coat the inside of the tank.

The first thing you do is put a strong detergent in the tank with some water and then dump in a bunch of nuts and bolts (or plain 'ol gravel. Then you put the cap on the tank and pick it up and shake the hell out of it every time you walk by it. Repeat this procedure as many times as it takes for the water to be clean when you dump it. Then comes the acid treatment, and then the "sloshing" exercise to coat the inside of the tank.

It ain't much fun, but it works. But .... if the tank were mine I'd take it to a radiator shop and say "Fix it". They can. They'll also patch any pin-hole leaks that may have been caused by the rusting.

Good luck,

Jim
Yes there are gas tank coatings, for tank insides, and there probably the same chemicles. the acid is more than likely a very light Myriatic acid that will eat the rust but eat the metal much slower but could if left in too long ( week or so ).