you have to seal that shit!!! i did a 3 step process on my maxi. the cleaner... the acid and then the silver metallic coating that fills and seals the tank from rusting again. it also neutralizes any future oxidation. Do it. you will be happy you did
it is by POR 15 US standard fuel tank sealer!
here is the link to the website. your local auto paint store should carry this.
<url>http://www.imperialrestoration.com/products.php?category=14<url>;