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

Abstract

A series of six austenitic alloys has been prepared in which the nickel content was successively increased from 14 to 78% while retaining a base level of 20%Cr. These were isothermally exposed for 100 hours at 700°C in an air–45% water vapour environment, an oxidising–sulfidising environment (air+49%Ar+26%H2O+1%SO2) and a chlorinating environment at low oxygen partial pressure (argon+0.1%O2+15–26%H2O+0.2–0.35%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.