Originally posted by: NinjaJedi
Copper does not rust. It does oxidize. I wouldn't worry. The only way I know to restore copper without a compound is to use coca cola. Probably not a good idea since it would be hard to clean all the surfaces without soaking it completely. Done carefully it could be done though. Just clean after with water. Also handling copper with bare hands will make it oxidize faster due to oils from the skin. I used to clean my beryllium ping eye 2 golf clubs with coke and they would look new again for about a week.
Rust is iron oxide, patina is copper carbonate (green, think Statue of Liberty which is green but made of copper).
Iron will react with oxygen dissolved in water to form iron oxide (rust, reddy colored).
Copper will react with CO2 (in the atmosphere) and water/moisture to first form carbonic acid (CO2 + H2O -> H2CO3) which subsequently reacts with the copper surface to form patina (copper carbonate, greenish in color when thick enough).
Coca cola contains phosphoric acid, H3PO4, which reacts with CuCO3 and dissolves it, leaving behind the neutral copper metal which was previously covered by the surface layer of CuCO3. Once the new surface of copper metal is exposed the process starts over again.
Copper oxide will form in competition with the formation of copper carbonate, but it is not the prefered oxidation species when CO2 is present (as our fossil fuel driven global economy ensures...).