THE INFLUENCE OF AERIAL OXYGEN ON THE INTERACTION OF POLYCRYSTALLINE SILVER SURFACES WITH SO_2 CONTAINING HUMIDIFIED AIR

摘要

Air pollutants such as sulphur containing gases (SO_2, H_2S etc.) play an important role in atmospheric corrosion and degradation of silver. The role of an SO_2 containing atmosphere with high humidity content on the initial atmospheric corrosion of polycrystalline silver surfaces was investigated under in-situ conditions using Quartz Crystal Microbalance (QCM) and Tapping-Mode Atomic Force Microscopy (TM-AFM). Additionally, ex-situ measurements could be performed with Time Of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). These methods enable the detection of corrosion layer formation, the sample surface morphology, and chemical assembling of weathered samples. The investigations revealed, contrary to earlier assumptions, that silver is affected by SO_2 in humidified atmosphere even in the absence of additional oxidizing agents. Furthermore, the formation and formation rate of silversulfite itself indicate a strong dependence on the presence of aerial oxygen. These results lead to the proposal of a new reaction mechanism for the sulfidation of polycrystalline silver surfaces exposed to humidified atmospheres containing SO_2.