I got a plastic tub, which I estimate to hold 12 gallons, and filled it with the appropriate mixture of water and soda ash (sodium carbonate). The grocery store had a nice box of Arm&Hammer Washing Soda in the detergent isle. I applied power, and watched for smoke! It was eventful enough to get some nice bubbles form on the electrodes as the variac was dialed up to 3 amps DC current drain from the tank. Now I just watch and wait while chemistry takes the labor out of rust removal.
|Witches brew of ions and oxides|
The results were rather good. The old paint and rust just came right off after about 24 hours of electrolysis. The anodes needed scraped clean every so often as the current dropped off due to the increased resistance. After removing the grill from the tank, the smallest pits of the original casting were free from rust. I was pleasantly surprised. The wire brush took care of the rest of the residue with a minimal amount of scrubbing. The resulting "black rust" magnetite conversion scrubs right off. I shot the grill with a quick coat of primer to avoid any more red iron oxide rust. The whole surface will need to be glazed and sanded with a fine grit to eliminate the appearance of any pits once the top coat is applied.