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so, I was at the remote cabin over the weekend. Adding to all the other work I had to do in the whirlwind weekend stay there, I managed to address the cleaning of the now dropped M37 fuel tank.

When I left the cabin 2 weeks ago, I had dropped the tank, and drained off the old fuel and left it outside to dry out.

When I arrived, the tank was bone dry, and all the rusty sediment just came out by dumping it out thru the now open filter access panel. I even pounded along the outer surfaces a tab with a mallet to loosen any other chunks if there were any....I got about two-three handfuls of rusty scale and powder.

I then flushed with garden house while upside down on saw horses until the water ran clean.

My initial plan of attack was to stop there, bring it back home to Dallas with me and bring to a radiator shop to boil out. then begin the three step gas tank reline process.

However, before I left Dallas to go up there, I read an article online where people have used muradic acid to clean a tank. and actually end the cleaning process there...

Thinking back on reline kits I have used in the past, I beleive the first chemical step was a solution of muratic acid. Anyway, I bought two gallons at home depot of muratic acid to take with me.

I poured the acid in the tank, let sit a few hours, rotated to each side, let sit a few hours, etc till I got just about all I could with two gallons inside. I even dumped a little in the fuel inlet and vapor inlet.

after all this time, I flushed it again. I was very surprised. the tank was near perfect inside, with slight pitting left on the baffles and what surfaces I could see. But its 10000 % better. I had no leaks so the tank is super solid.

I am thinking of ending the cleaning here.. no reline. I mean its so darn clean now its incredible.

Now I realize that there may still be some rust here and there on surfaces I didnt maybe hit well, or places I cant see. But am thinking that along with my new stainless steel cleanable filter I should be good to go.
I realize the tank will continue to rust without a reline job, but I am also thinking of giving this a try, as is, and see how it works out.

anyway, just an update for you guys... the muratic acid worked well for me....has anyone does this themselves and have comment on the process?

Word of caution should you use muratic acid.: wear rubber gloves and eye wear.. and do this outside with plenty of ventilation. DONT breathe in the fumes! anything spilled can be nuetralized with baking soda, so keep some nearby..

Another method that has been used by people I know is to add a couple of handfuls of damp sand to the inside of the tank, close it up tight and strap it to a cement mixer for a couple of hours.

The inside of the tank comes out spotless.

I would still have the inside of the tank coated. I just don't like doing jobs twice.

52 M-42

I wish I had a cement mixer

I agree however doing it once and be done with it is nice too.
However, I risk the chance of NOT doing it right and messing up a perfectly great tank.. I have heard stories of improper adhesion, bubbles or water left on the surface and the re-liner doesnt stick to the surface and peels off in sheets.

I have used re-lining kits in the past, with good luck, but these tanks I had no choice.. they were SO RUSTED and had small holes and leaks... I had not much choice..

Ill see... I got time ..

52 M-42 wrote:Another method that has been used by people I know is to add a couple of handfuls of damp sand to the inside of the tank, close it up tight and strap it to a cement mixer for a couple of hours.

This.

I would still have the inside of the tank coated. I just don't like doing jobs twice.

And this.

If you don't get all of the rust out, and then re-line it with a good quality product, I think you'll have problems. Especially in a vehicle that will sit for extended periods of time.

I've had two M37 tanks redone by Gas Tank Renu, and wouldn't prep a fuel tank any other way now.

From what I have read the Muratic Acid will remove any galvanization that was on the metal. That will allow flash rust.

The next step if you buy a tank kit is to buy Phosphoric Acid and run that around in the tank to kill any flash rust and leave a Phosphate coating.

Next is to neutralize the Phosphoric Acid with Acetone. That will leave a nice rough Phosphate coating. Then you take the tank liner material and coat all the sides of the tank innards.

If you bought a good liner material that is 'resistant' to alcohol gas you will be good to go.

Alan