Degradation of Copper and Copper Alloys by Atmospheric Sulfur

The interaction of copper and its alloys with atmospheric sulfur gases occurs in many combinations and at many rates. This paper reviews the results of experiments conducted to determine which sulfur gases cause major copper and copper alloy degradation and to study the degradation rates of copper and its alloys during exposure to the corresponding gases. Of the gases that have been studied in this work, sulfur dioxide (SO2), hydrogen sulfide (H2S), and carbonyl sulfide (COS), cause major corrosive reactions with copper and copper alloy substrates. Temperature, relative humidity, the presence of ozone, and solar irradiation have accelerating effects on the reaction rates of the gases and substrates. Copper, brass, and bronze alloys were examined. Copper generally had the highest corrosion rates. Those of the brass alloys were 50 to 100 times less than those of pure copper, and the substitution of nickel for all or part of zinc further increased the corrosion resistance of the alloy to low and moderate exposures of corrosive gases.