Industrial General Purpose Metal Cleaner BC-4000. A general purpose alkaline metal cleaner degreaser that is vastly superior to solvents when prepping metal for painting. It is very economical as it this 9 parts water to 1 part cleaner for most metal cleaning applications. It is biodegradable and acts by emulsifying any grease and oil on the metal surface. Just spray or wipe it on and wash off with clean water or wipe off with clean, lint-free rags. BC 4000 is safe for use on all metals.