Stress Corrosion Resistance of Some Copper Base Alloys in Natural Atmospheres

This paper describes the results of a test program where 25 copper alloys were exposed as stressed U-bends to two industrial atmospheres and one marine atmosphere for times up to 8 years. Many of the alloys have not failed to date. However, a number of zinc containing alloys (>20%), even in the presence of other alloying additions which normally impart resistance to stress corrosion, have failed. The industrial sites are more aggressive than the marine site, resulting in failure of more alloys and shorter stress corrosion life. Alloying effects were found to be extremely important in determining stress corrosion susceptibility and crack morphology. The results are discussed relative to the influence of environment, alloy composition, and structure on stress corrosion performance and the mechanism of stress corrosion cracking (SCC).