METAL CARBOXYLATE FORMATION DURING INDOOR ATMOSPHERIC CORROSION OF CU, ZN, AND NI

Chemical analyses of surface films and corrosion products formed on pu re Cu, Zn, Ni, and Ag samples exposed up to 12 months in various mild indoor environments have been performed by infrared reflection-absorpt ion spectroscopy (IRAS) and x-ray photoelectron spectroscopy. The anal yses reveal metal carboxylates to be the main ingredients on the surfa ce of Cu, Zn, and Ni. Other ions, such as sulfate, chloride, nitrate, and ammonium ions are also present but in smaller amounts. The surface region on Ag contains mainly silver sulfide with smaller amounts of s ulfate ate, ammonium, and chloride ions. The growth of the carboxylate layers, as followed by IRAS, exhibits an initial film formation with a thickness of a few nanometers for all exposure sites investigated. S ubsequent growth to thicker layers was observed at sites with higher h umidity levels. The unexpectedly high content of metal carboxylates fo und on Cu, Zn, and Ni may provide insight into possible processes invo lved in the atmospheric indoor corrosion of these metals.