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Hi Guys
Just tackling a few things on my 1967 Bonneville project before I stash it while enjoying the summer and riding.

The Bonneville was last on the road in 1993 and after being parked, the remaing fuel was left in the tank.

I drained it and the gas had turned to a red liquid resin.

My question is what is teh best method to clean the tank?

I already took it to a rad shop to have cleaned, but he wouldn't touch it, as he thought it would stink up his shop.

Thanks
John

I’ve had great results with a few rinses of diluted muriatic acid, followed by a few rinses of Lysol Lime & Rust remover (black bottle toiler cleaner). Make sure to thoroughly flush the tank between each muriatic acid flush.

I'd start with petrol above the gum line, leave it for weeks, shaking occasionally. After all this was dissolved in petrol to begin with.

I'm doubtful that acid will have much impact on the resinous gum.

If that doesn't work, perhaps MEK? That cleaned most things in the nasty chemicals industry I once worked in.

Lacquer thinner and loose screws. Let sit, shake, let sit , repeat - until the crude is out. Then treat with phosphoric acid to get rid of rust, available at Home Depot in paint department. Keep the lacquer thinner away from the paint. You can use a less harsh thinner or hot soapy water that won't attack the paint if you aren't repainting.

Hi John, Acetone works well also. If you use any type acid tank will be very prone to rusting from now on.
It removes the tiny thin layer or tin plating from steel. It acted as lube in the press die.

All the strong solvents will damage paint instantly!!

If you want to save paint, use Kreem paint mask. 2 thick coats. Then cover that with Glad wrap. Use shorter sheet rock screws. 2#. Plug filler with rubber stopper from hardware store.

Final rinse with Acetone or lacquer thinner.

If you do good job with paint mask it 100% protects pain from acetone. Lacquer thinner I’ve never used.

If you get rusting down the road you have no choice but to install liner. I recommend Caswell.
Don

Phosphoric acid will remove the rust, it will also leave a thin coating of iron phosphate on the steel. Unlike iron oxide the iron phosphate is as dense as the steel and is a mild rust preventor.

Hi, I used Kreem tank cleaner kit. It was acid but didn’t damage paint. Then the flushing solution. It was acetone.

What acid it was I don’t know. Metal was bright silver after cleaning.

It rusted bad after cleaning. E10 fuel is all we can get. Bottom of tank didn’t rust. The air space above fuel looked like steel found laying on the sea shore in 2 years. Just horrible! Of course started leaking through rust pin hole. Caswell cured the leaks 4.5 years so far. So good.

Looking at Kreem part A acid it’s now phosphoric acid. Was it then? I don’t know. It indeed etched the metal. It did not leave full grey finish. It was shinny silver. I’m wondering if they’ve changed their part A from when I used it. My tank had zero rust, but I didn’t drain for storage. Filled to the brim. Fuel left thick hard coating like asphalt. Liquid smelled like paint thinner. The plan was store for 2 years only. It turned into 34!
Don

Yes, phosphoric acid is the choice for vintage auto sheet metal restoration.Ospho is a popular brand...My experience is the dark appearance of the treated steel...Normal after treatment procedure is a mineral spirit washing on surfaces to be painted....Ya,phosphoric acid is the magic but weak rust remover in Coca Cola,

I've had to use aircraft paint stripper to dissolve that gum in the bottom of the tank, also oven cleaner. Not quick either... KBS sealer and rust remover for the last ten or so years has been my favorite.

Phosphoric acid also will soak rust out of the pin-holes in a rusty surface.
Rinse with hot water, which will quickly air-dry, and you're done ... for the inside of a tank, anyway.

If de-rusting an outside surface, do the same then prime immediately after the part has dried.