Influence of Humidity, Sulfur Dioxide, Ozone and Nitrogen Dioxide on Copper

This thesis presents a new experimental setup for surface analysis studies, incorporating chemical information from infrared reflection absorption spectroscopy (IRAS) and quantitative information from quartz crystal microbalance (QCM). The integrated IRAS/QCM surface analysis system enables in situ studies to be conducted of the metal/atmosphere interaction on a sub-monolayer level. In combination with topographical information from tapping mode atomic force microscopy (TM-AFM), it was possible to follow the formation of corrosion products providing information about chemical identity, quantity and lateral distribution. The newly developed system was used to study the influence of relative humidity (RH) and levels of sulfur dioxide (SO2), ozone (O3) and nitrogen dioxide (NO2) down to concentrations of sub parts-per-million (ppm), on the initial stages of atmospheric corrosion of copper. Exposure to RH led to the formation of small grains of cuprous oxide (Cu2O), with an average diameter of approximately 40 nm. The grain nucleation rate increased with increasing RH due to the increasing amount of physisorbed water on the surface. Exposure to RH and SO2 led to the formation of copper sulfite (CuSO3•xH2O) species as well as reduction in the rate of Cu2O formation. The formation of CuSO3•xH2O occurred through the dissolution and consecutive precipitation of surface-bound copper sulfite complexes. The roles of O3 and NO2 in the SO2-induced atmospheric corrosion of copper was also investigated. O3 was found to have a two-fold effect, resulting in the oxidation of the copper sulfite species to copper sulfate and the enhancement of Cu2O formation. NO2 promoted the oxidation of copper sulfite species, though less efficiently than O3, and reduced Cu2O formation. In addition, copper nitrate formation was observed. IRAS was also used to investigate the interaction between SO2 and surfaces made of platinum and palladium. Sulfuric acid formation was observed on both metals, showing the importance of the surface on the formation of the metal/atmosphere reaction products.