About the Formation of Basic Silver Carbonate on Silver Surfaces – An In Situ IRRAS Study

Air pollutants such as carbon dioxide play an important role in atmospheric corrosion processes and therefore in the degradation reactions occurring on metal surfaces exposed to an ambient atmosphere. It is known from macroscopic studies that ultraviolet (UV) light influences these surface reactions with respect to the reaction rate and the product formation itself even though the exact mechanisms have not been elucidated in situ at a subm level so far. Therefore, the role of CO2 in the humidified ambient atmosphere and the influence of UV light on the initial atmospheric corrosion behaviour of silver surfaces were investigated under in situ conditions using a combined InfraRed Reflection Absorption Spectroscopy (IRRAS) and Quartz Crystal Microbalance (QCM) set-up. To obtain 3-dimensional information about the depth distribution of the corrosion products formed, ex situ Time of Flight Secondary Ion Mass Spectrometry (TOFSIMS) measurements were performed additionally. The investigations revealed in situ the main and intermediate reaction products during the formation of basic silver carbonate on a polycrystalline silver surface. Furthermore, a strong dependency of the product formation rate with respect to the CO2 concentration and the humidity content in the ambient atmosphere as well as the influence of UV light irradiation of the surface could be demonstrated.