Gas Tank Refurbishment
 

After 8 months of distractions, I am circling back around to my factory auxiliary fuel tank. I have acquired the parts I think I will need. The tank was badly damaged from a failed filler hose not taken care of, allowing water and dirt from the bed to flow into the tank. The feeder lines were capped off so no issue with contamination into the main system. Cutting an inspection hole, the tank was pretty badly rusted inside, but not so much as to compromise the integrity of the tank. I used a Harbor Freight sand blaster to clean things up as best I could considering I was squirting blind in the tank. It will need a little more work to finish descaling to an acceptable condition. I have searched and found a few tank treatment kits. Can I get any recommendations from those that have used these kits and how scaled was your tank prior to use.

Re: Gas Tank Refurbishment
 

You could get a few gallons of molasses from a feed store, or some concrete etch phosphoric acid from the home store and let it soak for a time while rotating the tank occasionally. Molasses will take weeks and PA a few hours. Both should be diluted. Add gravel for an abrasive. Don't get the PA on concrete--it will dissolve.
I did something similar with a tank flush and made a wooden frame to help with the rotation. Being lazy I might motorize the rotation bit if I had to do it again.
I can't comment on the coating stuff since the tank is still waiting to be used.

Re: Gas Tank Refurbishment
 

If you can find an old school radiator repair shop, they can sometimes provide great service on cleaning out and treating old tanks like this. As for the DIY kits, I used this one on an old Massey Ferguson 50 tank a few years ago and it sealed/worked well. It was important to roll it around and get all inner surfaces coated. You'd need two of these for a truck tank. And I'm sure there are plenty of other options out there as well that other folks will have had good experiences with. One of the nice thinks about this goop is it's tinted blue, so with a small mirror and a bright light, you can actually tell how well you've coated the inside.

EDIT: ok, well, crap... it says not for sale in CA (sorry) and I see that's where you are - but there is a note about a low VOC alternative they sell to CA residents.