LD7铝合金阳极氧化膜的不同封闭方法耐蚀性评价

EVALUATION OF SEALING METHODS ON CORROSION BEHAVIOR OF LD7 ALUMINUM ALLOY ANODIC OXIDE FILMS IN NaCl SOLUTION

研究了不同封闭方法对LD7铝合金阳极氧化膜在NaCl溶液中耐蚀性的影响,包括沸水封闭、氟化镍封闭、重铬酸钾封闭和醋酸镍封闭.利用动电位极化和电化学阻抗谱(EIS)研究了封闭后阳极氧化膜的腐蚀行为.利用扫描电子显微镜(SEM)观察了封闭后阳极氧化膜的表面形貌.结果表明在酸性溶液和碱性溶液中醋酸镍封闭能提供更高的耐蚀性,而沸水封闭在中性溶液中较耐蚀.工业生产中普遍采用的重铬酸钾封闭对LD7铝合金阳极氧化膜封闭效果并不理想,封闭后的阳极氧化膜在不同pH值的溶液中耐蚀性均不高,氟化镍封闭的阳极氧化膜层耐酸性不强.

Potentiodynamic polarization and electrochemical impedance spectroscopy （EIS） were used to study the influences of sealing methods on the corrosion behavior of anodic oxide film on LD7 aluminum alloy in NaCl solution. The anodic oxide films were sealed by the methods of boiling water, nickel fluoride, potassium dichromate and nickel acetate, respectively. The surface morphology was examined by scanning electron microscopy （SEM）. The results show that nickel acetate sealed film provides relatively higher corrosion resistance both in acidic and in basic solutions, while boiling water sealed film is better in neutral solution. Potassium dichromate sealing method, which is very popular in the industry, could not provide good sealing quality for anodic oxide film on LD7 aluminum alloy in acidic, neutral and basic NaC1 solutions.