Abstract:The corrosion behaviour of 7B50 aluminum alloy in simulative atmospheric pollutants solution was investigated using electrochemical methods. Ten different media were chosen based on common atmospheric pollutants, such as H⁺, Cl^-, NO₃^- and NH₃·H₂O, or the combination of them. Parameters, such as corrosion potential, corrosion current density, linear polarization resistance, pitting potential, repassivation potential, pit transition potential, and charge transfer resistance are obtained from cyclic polarization curve and electrochemical impedance spectroscopy (EIS). The results show that H⁺, Cl^-, NH₃·H₂O and OH^- are all corrosive substances which increase the corrosion rate of 7B50 aluminum alloy several times, respectively, while NO₃^- is a corrosion inhibitor in spite of being more corrosive when integrated with H⁺. According to the electrochemical parameters, the corrosive ability of several acids and alkali (1 mmol/L) in decreasing order is NH₃·H₂O, H₂SO₄, HNO₃, HCl. In addition, Cl^- reveals the weakest anodic polarization of electrode when comparing with other ions, which means it has the highest anodic current density. Also, the localized corrosion of Cl^- is the severest.

Key words: 7B50 aluminium alloy; atmospheric pollutant; electrochemical corrosion; cyclic polarization curve; electrochemical impedance spectroscopy