Long-term corrosion behavior of the 7A85 aluminum alloy in an industrial-marine atmospheric environment

The atmospheric corrosion behavior and mechanism of the 7A85 aluminum alloy exposed to the Qingdao industrial-marine atmospheric environment for five years was investigated using the weight-loss method, mechanical property analysis, morphology observations, scanning Kelvin probe force microscopy, and corrosion product analysis. The results showed that the mechanical properties of the exposed 7A85 Al alloy deteriorated considerably, which was mainly induced by pitting corrosion and intergranular corrosion. Al2CuMg and Al7Cu2Fe intermetallic particles were the main precipitates in the 7A85 Al alloy, and the particles not only induced a defective film but also acted as cathode phases in the precipitate-matrix galvanic corrosion couple, which led to pitting corrosion initiation during atmospheric corrosion in Qingdao. Moreover, intergranular corrosion initiated and then propagated owing to micro-galvanic corrosion along the grain boundaries.