LC4超硬铝合金微弧氧化膜电化学腐蚀特性

Electrochemical corrosion behavior of microarc oxidation film on LC4 aluminum alloy

用微弧氧化方法在LC4超硬铝合金表面获得较厚的氧化膜,测定了氧化膜的生长曲线及电流密度变化,并用电化学方法测定不同厚度膜的极化曲线,采用零电阻技术测量3.5%NaCl溶液中LC4铝合金-铜电偶对电偶腐蚀情况。用扫描电镜观察合金基体和微弧氧化膜的腐蚀形貌。经过微弧氧化处理后,LC4超硬铝的腐蚀电流密度比基体降低几个数量级,腐蚀电位上升,耐腐蚀性能得到很大提高,但膜超过一定厚度时腐蚀电流密度反而有所升高。较厚的微弧氧化膜大幅度降低了LC4/Cu电偶对的电偶电流,电偶电位正向移动。

A thick ceramic film was deposited on LC4 super-hard aluminum by microarc oxidation technique (MAO). The growth kinetics of film and evolution of applied current density were measured, The electrochemical method was employed to determine the polarization curves of the coated alloy with different film thickness. In addition, the galvanic corrosion of LC4 alloy coupled to copper in 3.5% NaCl solution was also evaluated by a zero-resistance technique. Scanning electron microscopy was used to analyze the corrosion morphology of the bare and coated alloy. After MAO treatment, the corrosion current density of LC4 alloy is reduced several orders of magnitude and the corrosion potential is increased, thus the corrosion resistance of the alloy is greatly improved through MAO treatment. However, the corrosion current density slightly increases while the film thickness is over a certain thickness. For the alloy sample with thicker film, the galvanic current of the LC4 alloy-copper couple is significantly reduced.