THE SULFIDATION OF 2-PHASE CU-AG ALLOYS IN H-2-H2S MIXTURES AT 550-750-DEGREES-C

The corrosion of three two-phase Cu-Ag alloys by H-2-H2S mixtures has been studied at 550-750 degrees C under sulfur pressures below the sta bility of pure Ag2S. In all cases the scales are duplex and contain an outer layer of pure Cu2S and an inner complex region composed of a mi xture of the Ag-rich metal phase and internal Cu2S particles. The micr ostructure of this region differs for the three alloys, but remains ve ry similar for each alloy at the three temperatures. The peculiar micr ostructures of the scales are discussed in the light of the presence o f the two phases in the alloys and of the restrictions which the limit ed reciprocal solubility of the two alloy components produces on the r ate of their diffusion in the alloy. Copyright (C) 1996 Elsevier Scien ce Ltd.