| The tarnishing mechanism of silver strip was studied by SEM, XPS, XRD . The results showed that a layer of white mist was formed on the surface of silver band during the condition of atmospheric annealing, which was mainly Ag2O . At the same time, some discontinuous black dots can be observed at the grain boundary. The main components are Ag, C and O. The surface of silver strip placed for a long time in air conditions will lose metallic luster to becomes gray, and had dark scattered spots which have no obvious growth characteristics in partial areas. The elements of C, Cu, Fe, Na, Mg are easily stayed in the surface of the silver strip during the machining process, while these residual elements are not the main factors causing silver strip tarnishing. The main reason of tarnishing was silver strip reacting with hydrogen sulfide, sulfur dioxide in the air, and the corrosion products mainly include Ag2S, Ag2SO3, Ag2O. |
