Initial oxidation of silver surfaces by S2−and S4+ species

Silver has been exposed to each of the sulphurous gases under the influence of different humidity contents in the ambient atmosphere and in the presence and absence of aerial oxygen. The samples were investigated by means of in situ quartz crystal microbalance (QCM), tapping-mode atomic force microscopy (TM-AFM) and time of flight secondary ion mass spectrometry (TOF-SIMS) which enables to characterize the corrosion layer formed, the morphology and the chemical structure of the weathered surfaces. The investigations revealed that sulfidation by both gases is strongly dependent on the relative humidity (% RH) content and the aerial oxygen content in the ambient atmosphere. The results obtained are used to suggest new mechanisms for the sulfidation of silver surfaces exposed to humidified atmospheres with addition of SO2 and H2S, respectively.