I've got a little RolAir 2 or 3 gallon pancake that I've had for eons (it was my Dad's and he had it for as long as I could remember). Recently the tank rusted through and started leaking.

I found an ad on kijiji for an old campbell hausfeld two-piston compressor with no motor. I went out there tonight and ended up scoring the tank, two pumps, two pressure switches, and a regulator for fifty bucks. No idea if the tank leaks or what the internals are like, but for fifty bucks I'll deal with it. Both pumps have apparently been rebuilt (you can see new gaskets sticking out of at least one).

The guy said the tank was around 25gal, but is there a way to figure out the capacity by measuring it?

The only model numbers I could find are VT612100 and VT5108, neither of which bring up any info on Google. Anyone know anything more about this setup?

I'm either going to snag the pump and motor off the old RolAir and hook it up to this tank, or see if I can find a cheap motor to run one of the new pumps. Is there any way to figure out the HP rating I need? There's a tag that says '733RPM' somewhere..

Also, about rust on the inside of the tank - can I spray a bunch of fluid film in there and shake it all around to try to quell whatever rust is growing? The drain was open when it was stored and I don't know if that's bad or good. Will having oil inside the tank contaminate my tools (I'm thinking like sanding and possibly spraying paint somewhere down the line).

Thanks for any info (sorry for the longassed post)