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在含有磷酸钠和钼酸钠的电解液中采用恒流模式对5083铝合金进行微弧氧化。研究了电流密度对氧化电压、膜层生长速率的影响;采用扫描电镜和能谱对氧化膜的表面形貌和成分进行了分析;采用电化学极化曲线测试了氧化膜的耐腐蚀性能。结果表明:在恒电流微弧氧化过程中,氧化电压出现直线快速增长和平稳增长两个阶段,且随着电流密度的增加电压逐渐增大;随着电流密度的增大,氧化膜厚度增加,其表面微弧放电产生的微孔数量逐渐减少,而“火山堆积”状形貌特征越来越明显,电流密度过大氧化膜出现局部剥落,其对氧化膜成分影响不明显;微弧氧化陶瓷膜提高了铝合金基体的耐腐蚀性能,当电流密度为7.5 A/dm2时,微弧氧化膜的自腐蚀电流为1.9×10-8A/cm2,比铝合金基体降低了1个数量级,表现出良好的耐腐蚀性能。
In the electrolyte containing sodium phosphate and sodium molybdate, the 5083 aluminum alloy was micro-arc oxidized by the constant current mode. The effects of current density on the oxidation voltage and film growth rate were investigated. The surface morphology and composition of the oxide film were analyzed by SEM and EDS. The corrosion resistance of the oxide film was tested by electrochemical polarization curve. The results show that in the process of constant current micro-arc oxidation, the oxidation voltage appears in two stages of linear growth and steady growth, and the voltage increases with the increase of current density. With the increase of current density, the thickness of oxide film increases, The number of micro-pores generated by micro-arc discharge on the surface gradually decreased while the characteristics of “volcanic heap” shape became more and more obvious. The current density was too large, and the oxide film partially peeled off, which had no obvious effect on the oxide film. Oxidation ceramic film improves the corrosion resistance of aluminum alloy substrate. When the current density is 7.5 A / dm2, the self-corrosion current of MAO film is 1.9 × 10-8 A / cm2, which is 1 order of magnitude lower than that of aluminum alloy substrate. Show good corrosion resistance.