The Effect of Cyclic and Constant Thermal Exposure on AA5083 and Related Alloy Susceptibility to Intergranular Corrosion

AA5083 family of alloys are the most widely used alloys for marine application. However these alloys are susceptible to intergranular corrosion (IGC) at high temperatures when they experience severe thermal cycling. In this work we investigated the effect of constant thermal exposure and thermal cycling on corrosion performance of these alloys. For a comparative purpose AA5456 and AA6061 alloys were also studied along with AA5083 alloys with different temper designation O, H116 and H321. ASTM-G67 tests were conducted on the heat treated alloys to measure their susceptibility to intergranular corrosion. Constant exposure tests showed a steady rise in mass loss with the increase of thermal exposure time. Thermal cycling tests were also carried out by exposing the samples at 43°C and 70°C for different number of cycles. It was observed that samples exposed at 70°C were susceptible to intergranular corrosion. However, no such evidence of extensive corrosion was observed for those samples exposed at 43°C. In addition mass loss test results for thermally exposed samples at constant temperature was compared with the corrosion behavior of cyclically exposed alloy samples.