Stress Corrosion Cracking Control Measures. 4. Aluminum Alloys,

摘要

The most prevalent form of SCC service failures in aluminum alloys is caused by a combination of water, aqueous solutions or atmospheric moisture, alloy of susceptible composition and structure, and sustained tensile stresses, most often caused by heat treatment or assembly. The principal practical measures to control SCC are: (1) select an alloy of minimum susceptibility; (2) for wrought alloy, take precautions not to impose high sustained stresses across the short transverse grain direction unless the alloy and temper confer low susceptibility; (3) keep water and water vapor from the metal surface by providing natural drainage and by painting, with an inhibitor such as chromate; (4) minimize opportunities for chlorides to concentrate; (5) when using a susceptible alloy and temper, compressively stress the metal surface by peening or rolling, followed by painting; (6) use cathodic protection; (7) do not permit mercury or its compounds in close proximity to any aluminum structure.