My local general store has a pretty good paint department, and I found oxalic acid there in the form of a gallon of Cabot Problem Solver Wood Cleaner for $20. I realize there are probably cheaper ways to get OA, but I went the easy route. The gallon is intended to be mixed with 4 gallons of water to make a solution to clean tannin stains and nail rust from decks. I poured some of it straight into a baby food jar and then added all the bits from a very rusty pair of quick-release skewers (except the rods) and let it sit overnight. When I came back to it, the parts were covered in a pale green film which fell off with agitation. I pulled out the parts and rinsed them in the sink and they gleamed! The instructions said that the cleaner can be rinsed off the deck, so I had no qualms about dumping my undiluted spent OA down the drain. The only downside, which can not be helped, is that the chrome was still pitted, but that had nothing to do with the treatment process.