| Abstract: | Selective corrosion of copper-zinc-alloys Starting from recent ideas on the mechanism of corrosion the most important parameters – with respect to materials properties and water chemistry – of dezincation, pitting and intercrystalline corrosion of CuZn alloys are explained. Dezincation is increased if the alloy contains β-phase (duplex brass). Within certain limits of chloride and sulphate content dezincation of these materials can be prevented by an increased hydrogencarbonate concentration of the medium. At pure α-brass dezincation is preceded by local cestruction of the natural protection layer. Intercrystalline corrosion occurs preferentially at α-brass if the material contains precipitations at the grain boundaries. Intercrystalline attack is favoured by higher temperatures, coarse-grained microstructure, higher contents of the alloying elements arsenic and phosphorus as well as from the water-side by ammonia and the activity of aeration elements. |
