I am using a dc welder in a tank that is about 500 gal to experiment for complete cab dunk. [cab tank is 7x7 foot by 6 ft deep] grin .Small parts; inner fender,grill shell,rad support have had welder set 40-48 volt, 20-60 amp flow depends on size of part and how close to annode.some parts rinse off to bare steel some still have black iron after 24-30 hours :confused: .Has anybody else done this size.I cant figure out why some parts come out bare steel yet others have patches of black iron :confused: .Would heat have anything to do with this? I am using sodium carbonate,with sheet steel for annode.