大气污染物对7B50铝合金电化学腐蚀性能的影响Effect of atmospheric pollutants on electrochemical corrosion behaviour of 7B50 aluminium alloy

 以0.1 mol/L的Na₂SO₄为支持电解质，分别添加微量(1~10 mmol/L)的H⁺、Cl^-、NO₃^-、NH₃·H₂O及其离子组合作为模拟常见大气污染物的腐蚀介质，研究7B50超高强度铝合金在腐蚀介质中的电化学腐蚀行为。采用循环极化曲线和电化学阻抗谱，得到不同腐蚀介质中的自腐蚀电位、自腐蚀电流密度、线性极化电阻、击穿电位、保护电位、点蚀转换电位及电荷转移电阻等参数，表征不同离子的侵蚀性能及其之间的相互作用。结果表明：微量的H⁺、Cl^-、NH₃·H₂O使腐蚀速率增大数倍；1 mmol/L酸碱的侵蚀能力由大到小的顺序依次为NH₃·H₂O、H₂SO₄、HNO₃、HCl；NO₃^-单独存在时具有缓蚀效应，与H⁺结合产生加速腐蚀的协同作用；Cl^-存在下，电极的阳极极化程度最低，极化电流最大，局部腐蚀的发展程度也最大。

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.

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