Atmospheric corrosion of copper in the presence of acid ammonium sulfate particles

Basic copper sulfates, CuxSO4(OH)(y), and cuprite, Cu2O, are the major corrosion products found during field exposure of copper. The active species of the atmosphere which lead to formation of these corrosion products are, however, still uncertain. In this study, we investigated whether submicron acid ammonium sulfate particles, NH4HSO4, can lead to formation of a patina with the above composition. The corrosion process was followed by various analytical techniques, including in situ analysis by X-ray diffraction, pH, and scanning Kelvin probe measurements. The main corrosion products found at 300 K are mixed ammonium copper sulfates, (NH4)(2)Cu(SO4)(OH)(2) . cH(2)O, and small amounts of cuprite, Cu2O Those formed at 373 K are antlerite, Cu-3(SO4)(OH)(4), and cuprite Cu2O. From the room temperature results, NH4HSO4 does not appear to be responsible for patina formation. The corrosion mechanism is discussed and compared to that of copper with (NH4)(2)SO4 particles, which has earlier been shown(1,2) to lead to the corrosion products found in field exposed copper.