The cathodic deposition (CD) technique is widely used as a surface treatment technique to prepare surface protective layers for non-valve metals. However, due to the presence of dense oxide film on the valve metal surface, the dense oxide film will hinder the contact between the ions in the electrolyte and the substrate surface during the cathodic deposition process, making the cathodic deposition technique unsuitable for valve metals. In this paper, the valve metal AZ31 Mg alloy was first treated by micro arc oxidation (MAO) technology, and then CD treatment was carried out using ethylene glycol organic solution as the electrolyte. This method not only solves the problem that CD technology cannot be applied to valve metals, but also successfully prepares coatings with excellent friction and corrosion resistance, and explores a new solution as CD electrolyte. Hongkang Pan a, Honghua Hu b, Zhonghua Wei c, Fan Yang a, Zhanshuai Fan a and Hailin Lu a, *.Investigation on surface properties of AZ31 magnesium alloy modified by micro-arc oxidation and cathodic deposition techniques.[J]. Surface and Coatings Technology (Impact Factor: 5.4, CAS I).

Fig. 1 (a1) (b1) and (c1) show the macroscopic images of O, OW and OE samples, respectively. (a2) (b2) and (c2) are SEM images of O, OW and OE samples at 200× magnification, and (a3) (b3) and (c3) are SEM images of O, OW and OE samples at 1000× magnification, respectively. (a4) (b4) and (c4) are surface 3D contour images of O, OW and OE samples, respectively.

Fig. 2 (a) shows the macroscopic image of magnesium discs and SEM image with 200× magnification, (b) shows the macroscopic image of magnesium discs after cathodic deposition directly in deionised water solution and SEM image with 200× magnification, and (c) shows the macroscopic image of magnesium discs after cathodic deposition directly in ethylene glycol solution and SEM image with 200× magnification.