Cleaning aquaeous parts cleaner

I tried this on Moparts General, no luck.

I just picked up a heated, water based, parts cleaner at auction, it had been used in a factory to clean machined parts. Don't know why it is bothering me, but the tank is coated with some hard gunk.

Let me add a little. The washing tank is plastic and has splotches(almost complete coverage)of a hard gray film. It is almost like paint in thickness. In a few spots where I could get a scraper under it, it popped off. This doesn't mean it peeled off. So far I have tried Simple Green, Purple Power, wd-40, paint remover, acetone, lacquer thinner and PB Blaster.

Like I said, it was used in a factory and had plenty of metal chips in it. This might give someone a hint. I think it had the microbe/detergent in it before.

I have no idea what the stuff stuck to it is, but by your description it sounds like an Ozzy Washer... The microbials are in the Ozzy pad that needs regular servicing.. They arrive as unhatched microbials, the heat from the ozzy washer hatches them & if you shut the heat off they die.... And trust me they stink when they die... You also need to use Ozzy Juice in the tank to support their ecosystem.. They eat the oil & grease...

Didn't know the name, but I think it is an Ozzy Washer.