Investigations of the interactions of CO2, O3 and UV light with silver surfaces by in situ IRRAS/QCM and ex situ TOF-SIMS

The characterization of the reactions occurring during the atmospheric corrosion of silver surfaces at the metal-atmosphere interface is of great importance as only the exact knowledge of the degradation mechanisms enables the development of suitable corrosion inhibiting steps. For in situ surface analysis three complementary experimental techniques have been combined in order to study the surface chemistry of silver samples exposed to humidified air, CO₂, ozone (O₃) and ultraviolet (UV) light. In situ infrared reflection absorption spectroscopy (IRRAS) combined with a quartz crystal microbalance (QCM) as well as ex situ time of flight secondary ion mass spectrometry (TOF-SIMS) provide an overall picture of the processes occurring at the metal-atmosphere interface. Investigations were carried out by exposing polycrystalline silver samples to synthetic air containing 50-90% relative humidity (RH) and 250 ppm CO₂. Additionally, the samples were exposed to UV light or O₃ for certain time periods. The formation of the main corrosion products on the sample surfaces, depending on the relative humidity, O₃ content and UV light exposure could be observed in a time resolved way. These investigations reveal the different reaction mechanisms and reaction rates occurring on a silver surface.