TOF-SIMS investigations on weathered silver surfaces

Silver-coated quartz crystal microbalance (QCM) disks were treated under different environmental conditions (including changes in parameters such as relative humidity (%RH) and SO2/H2S content) in atmospheres of synthetic air and pure N2 for 24 h in a weathering chamber. The corroded surfaces were subjected to depth profiling by a time of flight (TOF) secondary ion mass spectrometry (SIMS) instrument, equipped with a Bi+ analysis gun and Cs+ sputter gun. The evaluation of the in-depth distribution of several elements and species provides evidence for the formation of a corrosion layer containing Ag2SO3, even in the absence of oxidizing agents, such as H2O2 or NO2. Furthermore it could be elucidated that the thickness of the formed Ag2SO3 layer does not depend on the SO2 concentration but rather on the humidity and oxygen content of the ambient atmosphere. In weathering experiments in atmospheres composed of synthetic air, humidity, and H2S, the presence of different oxygen species (surface and bulk) and silver sulfide could be detected by TOF-SIMS depth profiling experiments. The obtained results for both acidifying gases are in good correlation with the corresponding tapping mode atomic force microscopy (TM-AFM) investigations and in situ QCM measurements.