Comparison of Coating Properties by Two Pulse Modes on Magnesium Alloy
Micro arc oxidation is an effective method to improve corrosion resistance of magnesium alloys and the selected electric parameters have great effects on coating properties. In this paper, the effects of the unipolar pulse and the bipolar pulse on surface morphology, chemical compositions and corrosion resistance were studied. When working voltage was higher than breakdown voltage, sparks appeared on sample surface whether the unipolar pulse or the bipolar pulse was used. However, under the same positive working voltage, the spark size and lifetime obtained by the bipolar pulse were evidently larger and longer than those by the unipolar pulse, which resulted in rougher anodic coatings and worse corrosion resistance by the former than the latter.
Yafang Han et al.
R. F. Zhang et al., "Comparison of Coating Properties by Two Pulse Modes on Magnesium Alloy", Materials Science Forum, Vols. 546-549, pp. 585-588, 2007