大氣污染物對7B50鋁合金電化學腐蝕性能的影響Effect of atmospheric pollutants on electrochemical corrosion behaviour of 7B50 aluminium alloy

?以0.1 mol/L的Na₂SO₄為支持電解質，分別添加微量(1~10 mmol/L)的H⁺、Cl^-、NO₃^-、NH₃·H₂O及其離子組合作為模擬常見大氣污染物的腐蝕介質，研究7B50超高強度鋁合金在腐蝕介質中的電化學腐蝕行為。采用循環極化曲線和電化學阻抗譜，得到不同腐蝕介質中的自腐蝕電位、自腐蝕電流密度、線性極化電阻、擊穿電位、保護電位、點蝕轉換電位及電荷轉移電阻等參數，表征不同離子的侵蝕性能及其之間的相互作用。結果表明：微量的H⁺、Cl^-、NH₃·H₂O使腐蝕速率增大數倍；1 mmol/L酸堿的侵蝕能力由大到小的順序依次為NH₃·H₂O、H₂SO₄、HNO₃、HCl；NO₃^-單獨存在時具有緩蝕效應，與H⁺結合產生加速腐蝕的協同作用；Cl^-存在下，電極的陽極極化程度最低，極化電流最大，局部腐蝕的發展程度也最大。

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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