Quartz Crystal Microbalance (QCM) study of corrosion behavior of silver and simple corrosion test using sulfur vapor

Quartz Crystal Microbalance (QCM) technique was employed to continuously detect extremely small mass changes during corrosion of silver by sulfur vapor originated from sulfur flower as a function of temperature, RH and distance from sulfur to the silver surface. Corrosion progressed linearly with exposure time during all the tests. The corrosion rate increased as temperature rose, while no significant dependence on RH was observed. Furthermore the corrosion rate decreased markedly with increasing distance. This suggests that diffusion of sulfur vapor to the silver controls initial sulfide formation of silver. These results have led us to propose a simple corrosion test using sulfur vapor to simulate corrosion of silver during indoor exposure of electronic equipment. The test employs the two distinct characteristics of sulfur vapor test using sulfur flower. Firstly the vapor pressure of sulfur by sulfur flower varies widely with temperature resulting a wide range of sulfur concentration. Secondly the corrosion rate of silver in sulfur vapor can be controlled by varying the distance between the sulfur flower and the silver surface. Since the corrosion by sulfur vapor follows the linear kinetics similar to those found in practice as well as to provide identical major corrosion chemistry and morphology of the corrosion product, silver sulfide as in practice, we propose it to provide a reasonably reproducible, more flexible test which is much easier to handle in the laboratory than flowing multi-component gas mixtures containing hydrogen sulfide.