Exfoliation corrosion of extruded 2024-T4 in the coastal environments in China

Exfoliation behavior of extruded 2024-T4 in four coastal environments was investigated by the field testing and laboratory-accelerated test. At the Wanning, Qionghai and Qingdao test sites, exfoliation appeared on 2024-T4 after 6, 10 and 20 years exposure, respectively. At the Guangzhou test site, 2024-T4 did not suffer exfoliation after 20 years exposure. In the laboratory-accelerated test, the effects of relative humidity, temperature and Cl− amount on exfoliation were studied. Exfoliation could not occur on extruded 2024-T4 when RH was below 75%. Above this RH, the higher the temperature or the Cl− amount was, the more serious exfoliation the specimen suffered.

► Exfoliation behavior of extruded 2024-T4 in four test sites in China was studied.
► We studied exfoliation kinetics under various RH, Cl− amount and temperature.
► The critical RH of exfoliation was 75%, while exfoliation was slight when RH was 97%.
► Exfoliation became serious with the increasing temperature and Cl− concentration.
► The laboratory-accelerated test could well account for the results of the field test.