Abstract
Although it is widely recognized that copper alloys are subject to sulfidation upon exposure to the atmosphere, the information available on the sulfidation rates of these alloys has come largely from field exposures under uncontrolled conditions. To gain more definitive information on the rates and processes involved in atmospheric sulfidation of copper alloys, we exposed nine copper alloys (brasses, nickel‐substituted brasses, and other common compositions) to low concentrations of hydrogen sulfide in humidified air. Among the specific results are the following. (i) The resistance to sulfidation of the brasses was 50–100 times better than that of pure copper. (ii) The substitution of nickel for part or all of the zinc produces alloys even more resistant to sulfidation for low to moderate exposures; at longer exposures their behavior is mixed. (iii) Beryllium copper and phosphor bronze are somewhat more resistant to sulfidation than copper except for long exposures, when all three behave similarly. (iv) A silicon bronze sulfidized more rapidly than copper for most exposure periods. (v) Alloying copper with 10% aluminum yields an alloy with a sulfidation resistance nearly as good as the brasses. These results are discussed in conjunction with the information available on oxide growth on these alloys, and it is demonstrated that the sulfidation resistance of the alloys is quite similar to their resistance to oxidation, once an initial oxide film has formed. The degree to which the surface oxide film inhibits copper diffusion is thus reflected in the oxidation and sulfidation behavior of a given alloy. The results indicate that the performance in sulfidizing environments of equipment containing copper alloy components or parts can thus be markedly influenced by the particular alloys selected by the physical designer.