Storage of Metals
Source: Canadian Conservation Institute (CCI) Notes 9/2
Most metals corrode: iron rusts, copper turns green, silver turns black, and lead disintegrates into a white powder. Stored improperly, most of the metals in a museum collection will slowly transform into oxides, sulphides, carbonates, or other compounds. The corrosion processes are faster on metal surfaces contaminated by salts, volatile organic acids (such as those from wooden storage cabinets), ammonia from cleaning fluids, or dust. The rate of corrosion can also be increased through galvanic corrosion, a process that occurs when objects made of different metals are in contact with each other in high relative humidity (RH) conditions. (For more detailed information, Selwyn 2004.)
For best protection of metal artifacts, museum storage areas must be clean and well-organized, have controlled RH, and have as clean air as possible.
This Note describes general guidelines for the proper storage of metals. It explains the role of RH, recommends general storage conditions and handling procedures, and discusses a few specific metals: aluminum, copper, iron, lead, plated objects, and silver.