Cleaning inside air compressor tank

Bought this 120 gal. air compressor tank at a farm auction about ten years ago. Stored in a shed there and later in my garage. Project got cancelled after I bought a new IR compressor, so it's now for sale.

Popped all the plugs and gave it a good pressure wash inside. There was over 1-1/2 coffee cans worth of rusty muck that drained out. Scary w/ that amount at first,thought it might be scrap. Seams, bungs and walls look okay except for some stubborn rust on the bottom that the pressure washer won't remove. I think it's more lack of good position w/ the wand than bad, bad rust for removal.

I think this tank can be salvaged and put back in use after hydrotesting but I still wanna remove the remaining rust before selling. Registered National Board, rated 200 PSI., tag says about .200" wall thickness so the rust issue doesn't scare me... yet. There was plenty signs of oil in the washouts also.

This guy has the trick set-up for tank cleaning... but I ain't got no pipe machine at home. https://www.youtube.com/watch?v=pSFr4hJZPn0 (pipe machine starts at 6:15).

Although limited at home, I like the pea gravel w/ media added. Was hoping to find a pneumatic vibrator at work to attach to the tank and vibrate the media inside but no dice. I could put the tank on my lawn trailer and tow behind my tractor... for days. Don't wanna go the Muriatic Acid route unless I have to.

Any idears?

I've got a similar situation. I was given an ancient 2-stage compressor (blown up pump), 220v 5hp motor, with a 100 gallon tank. I estimate it is at least 60 years old and was run a lot. The old man ran it at 160 psi for decades. He was pretty good about maintaining it, so it was drained every day. But I'm still nervous about that much volume under pressure in an old tank. I plan on yanking the motor and scrapping the rest.

I bought an old compressor just for the tank as well a couple of years ago. What I did was get some "rust remover" liquid. I use that same acid that is sold for etching concrete. Phosphorus acid is what it is. Mix 1 part acid to 4 parts water and pour into the tank. Add some golf ball size rocks and some old nuts and bolts and seal up. Now you have to shake & roll the tank then let it sit for a while and repeat as often as you can. The longer you do it the cleaner you will get the inside of the tank. Once you drain the tank add some water and baking soda and flush the tank out. Let it dry and then what I did was coat the inside of the tank by mixing up some epoxy metal primer and poured it into the tank and then sealed it up and rolled it around to coat the entire inside. Pour out the excess paint and let dry. Done!

If you're worried and won't blame me if anything goes wrong, maybe you can rig up the pressure washer to do an at home hydro test, just make sure to get ALL the air out before pressurizing it.

It also looks a lot like a future BBQ to me.

I was thinking you could make a serious smoker with that thing.

Got to thinkin' more about this project last night. Labor intensive cleaning, possible liability if some shiny happy person blows it up, not worth the time or worry for slightly more money. While I'm all for saving/ refurbishing old equipment...

This tank would make an awesome BBQ/ smoker. From Google images:

Thanks guys for suggesting that.

Now for the asking price. $100 sound OK on CL? More/ less?