LD10铝合金微弧氧化膜的生长及腐蚀性能

Fabrication and Corrosion Behaviors of Micro-arc Oxidation Coating on LD10 Aluminum Alloy

采用双极性交流电源在LD10铝合金表面制备出微弧氧化膜。测量了硅酸盐电解液里微弧氧化膜的生长曲线,并分析了微弧氧化膜的结构、成分和相组成。采用浸泡腐蚀试验、醋酸加速盐雾腐蚀试验、动电位极化和电化学阻抗谱(EIS)方法评估了微弧氧化处理前后LD10铝合金的腐蚀性能。结果表明:LD10铝合金微弧氧化膜主要由γ-Al2O3组成,膜外层还有少量非晶相。微弧氧化初期,氧化膜主要以向外层生长为主,且表面粗糙度快速增加。随后膜层向内生长速度逐渐加快,最后阶段微弧氧化膜主要以向内生长为主。微弧氧化处理后LD10铝合金的腐蚀电位提高,腐蚀电流密度下降约2个数量级。微弧氧化膜的阻抗模值|Z|比铝合金基体大幅提高,同时其容抗弧半径远远大于铝合金基体。微弧氧化表面处理显著提高了LD10铝合金的耐腐蚀性能。

Micro-arc oxidation（MAO） coating on the LD10 aluminum alloy was fabricated in silicate solution by an AC bipolar power source. The growth curve of the coating was measured. The microstructure, composition and phase con- stituents of the coating were analyzed. The corrosion properties of the bare and coated LD10 alloy were compared by the immersion test, acetic acid accelerated salt spray test, potentiodynamic polarization and electrochemical impedance spec- troscopy （EIS）. The results show that： the MAO coating on LD10 aluminum alloy is composed of 7-Al2O3 and a small amout of amorphous phase. In the initial stage of micro-arc oxidation, the ceramic coating mainly grows toward the outer surface and meanwhile its surface roughness increases rapidly. Then, the growth rate of the coating toward the inner lay- er gradually increases. Finally, the coating mainly grows inwards. After MAO, the corrosion potential of the LD10 alloy increases and its corrosion current density decreases by about two orders of magnitude. The electrochemical impedance modulus ｜Z｜ of the coating is much higher than that of the bare LD10 alloy, and its capacitive loop radius is far higher than that of the bare LD10 alloy. Therefore, the MAO treatment significantly improves the corrosion resistance of the LD10 aluminum alloy.