I find a lot of 5 gallon buckets with some sort of brown epoxy stuck to the side and bottom. They work fine for holding bins for brass bearing, copper wire, etc. Tried chipping away some of the stuff, but usually just busted the bucket in the process. Steel drums might be a different story as far as taking a hammer and chisel to them. If you paint and label them on the outside, will the inside appearance matter that much to folks tossing in scrap?