Removing tarnish: I find NEVRDUL to be the best thing to clean up any kind of metal. I've used it on everything from chrome auto parts to brass fixtures. Available at auto stores, K Mart, etc. Coating to prevent further tarnishing: One of my daughters bought a product in a lighting store that works wonders. I had been having problems keeping a brass door plate free from oxidation and had used several products, none of which lasted more than 6-8 months. This product is simply rubbed on; at this point I am more than a year into it with no sign of the problem. When I ask her the name of the product, I'll post it.