Have you tried Kreem or other similar gas tank coatings? They have a multi-step kit for etching the metal on the inside of the tank, and then coating it to seal the metal so it won't rust further...
A handfull of small nuts, 50/50 mix of hydrochloric or muraticacid (sold as concrete cleaner at any hardware store) and water. Slosh it around for a while, then pour in some baking soda until it stops fizzing, that will nutralize the acid and make it safe to pour down the drain. Rinse well and use some sort of liner like kreem.
i thought about that as i was laying in bed last night thinking about the days activities... it dawned on me that they are small enough to cause alot of havoc down the road...[8D]