That rusty fuel tank trick...

[dougie]

You know the one. Shake it up with nuts, bolts, and grenades in it.
I remember that part.
I can't remember if it is done to a dry tank or with some fluid in it.

[She'llbe]

I took a couple of tanks to a powder coating outfit and they dipped the tanks in an acid bath and they came up great. rinsed them out with molasses or vinegar and I'm ready to apply an epoxy liner.

[CVA-42]

I've seen it done dry. If you do it, count the bits that go in and count them when they come out. My pal built an electric tumbler. Wrap the tank up, strap it in to the tumbler, flip the switch...

[Bamboo812]

Last time I did it dry with short lengths of chain, much easier to remove and I was only trying knock the loose stuff off. I wrapped it in blankets and packed it in a dryer with pillows to keep it from banging around. Rinse out with water, plug the petcock holes and fill with a 1:10 mix of molasses and tap water. Let sit for a few days, rinse and repeat if necessary. The vinegar will remove the red coating, but I'd be wary of using it for a long term soak. I've read somewhere that it will attack the brass in welds...

[dwerbil]

I used Kreem Koat on the /7 tank back in 1999. One part of the steps were to pour in the quart or so of diluted hydrofloric acid included and swish it around for some length of time. I felt it needed more of this treatment than what was supplied.

Checking at the local grocery store, there was a large bottle toilet cleaner with a 5% solution of hydrofloric acid. I bought three bottles, under ten bucks.

With petcocks removed and rubber stoppers in the tank holes, I poured in the three large bottles and topped it off with water. It sat for two days with an occasional shake around. After a through rinse out, the rest of the steps were followed.

It's now been going on 15 years and the Kreem Koat is still doing its job with no sign of separation.

I think the added acid etch helped the adhesion. The tank did not have a serious rust problem where it would had needed the nut and bolt scour routine.

[Garnet]

Acid man. Far out. (Battery acid)

Then rinse liberally with water and coat with your favorite goop.

[Major Softie]

Acid man. Far out. (Battery acid)

Then rinse liberally with water and coat with your favorite goop.

I would not use Sulfuric acid (battery acid) as a rust remover, especially on sheet metal: it is too fond of eating the metal as well. And, if I DID use it as a rust remover, I certainly wouldn't just rinse it off of sheet metal with water. I wouldn't think of painting it until I had actually neutralized the acid with something like sodium bicarbonate.

[Mal S7]

I would not use Sulfuric acid (battery acid) as a rust remover, especially on sheet metal: it is too fond of eating the metal as well.

Yes, sulfurix is a strong oxidising acid, from my chemistry I recall. You want something that will eat the rust, but not the metal. Phosphoric acid (coca cola) more better.

[dougie]

My plan is to do the nuts and bolts part first.
Then fill it with apple cider vinegar and let it soak I don't like playing with vicious chemicals.
http://www.youtube.com/watch?v=qUnYh6HM7x0

[Sibbo]

My trick is to use 1 part molasses and 2 parts water. It works beautifully to remove rust, deep or shallow but won't affect good metal.

I'd fill the tank with a molasses / water mix and leave it 2 weeks . The inside will be perfect.