Thought I would ask the bright minds here at thirdgen.

Bought a used compressor tank early in the summer... Only to realize it was not kept up very well.
I have a very thick watery/greasy mixture that also contains rust flakes. The sediment from rust can clog the 1/4" fitting in the bottom for the drain.
I had a bad experience with this tank, it was at a full 150psi and I went to drain it. Opened the valve and got nothing. Started to take the fittings off and got nothing. I took a screwdriver and poked it in to the bottom of the tank and yeah... The inside of the garage was covered, and I was covered and got lucky I didn't lose an eye.
After that, I did my best to rinse out the inside of this thing. Simple green, pressure washer etc. But, it still plugs the drain line. I have one of those stupid little threaded drain fittings on it, so I am going to be installing a ball valve for my drain set up.

I'm looking for what you guys suggest that I can use to break up the crud in the tank, like some form of an acid/water mix and then I can drain it.

I did paint with it in june/july time frame, had issues with the paint, but as far as I can tell those issues were all related to my gun at the time as I had some sections of the car that came out perfect.

I'm painting again in like a week or two, so I need some input!
I do run a 50' coil of hose and then a two stage oil/water seperator with a dissicant filter and another filter at the gun, so I'm decently set up there.

 

I'd send that tank to the scrap yard. Corroded pressure vessels are a safety hazard. Especially in the condition that you describe.

 

Can't argue with that logic.

I bought a used CH for the front garage, just for bike tires, portable air tank, etc. It had some rusty water in the tank, but no scale you you are describing. I cleaned it out as best I could, pulled the bung, and poured in a pint of POR15. Put the bung back in, rolled it all around to spread the product around, then drained the tank and left it to dry. That was 10+ years ago, and the accumulated moisture that I get out of the tank now is still pretty clean...not rusty like before.

 

If it has scale, it's not safe. It's a time bomb. Tic tic tic tic.......