三乙醇胺在镁合金阳极氧化中的作用

Effect of triethanolamine on anodizing process of magnesium alloys

在由KOH、Na2SiO3、Na2B4O7和三乙醇胺等组成的电解液中,以恒电流方式对AZ91D镁合金进行阳极氧化处理,并研究了三乙醇胺浓度对AZ91D镁合金阳极氧化膜层性能的影响规律。利用电压-时间曲线,全浸腐蚀实验、动电势极化曲线和扫描电镜(SEM)等方法检测和观察阳极氧化膜层的性能和表面形貌。实验结果表明:三乙醇胺可以有效抑制火花放电,增加膜层的厚度,使表面孔隙变小,提高表面光洁度;当三乙醇胺浓度为30g.dm-3时,膜层耐蚀性能最好;在阳极氧化过程中,三乙醇胺化学吸附于镁合金表面,从而改变微弧氧化过程中氧气气泡在镁合金表面的吸附强度和氧气气泡的大小,降低了微弧氧化陶瓷层孔隙率,提高了阳极氧化膜的致密性和耐蚀性。

The effect of triethanolamine concentrations on the properties of anodizing film of AZ91D magnesium alloy was investigated by using constant current anodizing technique in electrolyte containing KOH, Na2 SiO3, Na2 B4O7 and triethanolamine etc. Properties of the anodizing coatings were evaluated by voltage-time curves, corrosion rate and polarization curves and the coating morphologies were characterized by using SEM. Experimental results revealed that triethanolamine has remarkable effect on arc restraining, which resulted in an increase in the anodizing film thickness and a decrease in the surface micro-hole size, and finally the improvement in the surface finish. The anodizing film obtained by anodic oxidation in a solution containing 30 g · dm^-3 triethanolamine has good corrosion resistance. During the anodic oxidizing process, triethanolamine molecules are adhered by chemisorption to the surface of the magnesium alloy, through which the adsorption ability and the number of oxygen bubbles on the alloy surface decreased. Hence, the porosity of the obtained ceramic film is reduced, and the film density as well as its corrosion resistance is improved.