Effects of composition on the corrosion of Fe-Ni-Cr alloys in chlorinating and sulfidising environments

摘要

A series of six austenitic alloys has been prepared in which the nickel content was successively increased from 14 to 78 percent while retaining a base level of 20 percent Cr. These were isothermally exposed for 100 hours at 700 deg C in an air-45 percent water vapour environment, an oxidising-sulfidising environment (air + 49 percent Ar + 26 percent H_2O + 1 percent SO_2) and a chlorinating environment at low oxygen partial pressure (argon+ 0.1 percent O_2+15-26 percent H_2O + 0.2-0.35 percent HCl). The latter two environments gave opposite trends in terms of gross mass change. High metal loss associated with breakaway oxidation occurred at a low nickel contents in the chlorinating environment. In the sulfidising environment the most severe effects were observed at high nickel levels and were associated with the formation of sulfur-containing oxide nodules.