Corrosion behavior of copper and brass in serious Xisha marine atmosphere

Long period corrosion behavior of copper T2 and brass H62 after atmospheric exposure in Xisha islands for 3/4, 1, 2 and 4 a was investigated. The surface and cross-section morphologies, the elements distribution and phase compositions of corrosion products were observed by SEM, EDS and XRD, respectively. The results indicate that copper and brass undergo severe corrosion. The average corrosion rates for copper and brass in 4 a are 5.90 and 5.88 μm/a, respectively. The corrosion type of copper is uniform corrosion, a double layer structure is observed: a compact Cu₂O inner layer and a porous Cu₂Cl(OH)₃ outer layer. Dezincification processes with zinc preferentially dissolution are evident in brass, the zinc-rich corrosion products ZnO and Zn₅(OH)₈Cl₂·2H₂O are the predominating patina. Under the corrosion products, there exists a layer of pure copper originated from dezincification with the thickness of 20-50 μm.