The surface protection treatment of magnesium and magnesium alloys has important practical significance to enhance the corrosion resistance and expand its application field. Anodic oxidation is the most commonly used surface protection treatment for magnesium. Magnesium anode oxidation electrolyte is anodized layer protective performance is one of the decisive factors of using electrochemical testing technology and full immersion corrosion experiment method, the author has recently successfully developed on the basis of the green environmental protection electrolyte formula of new anodic oxidation process of film forming effect are compared with those of the classical process Dowl7 and HAE. It is found that the new technology can greatly improve the corrosion resistance of the material. In order to have a more comprehensive and in-depth understanding of the anodic oxide films formed under different technological conditions, the microstructure and comprehensive protective properties (including salt spray corrosion resistance, wear resistance and adhesion with the base metal) of the films obtained by different technological conditions were compared.

The experimental material was diecast magnesium alloy AZ91D, and its main chemical composition was (in wt%): A18.5-9.5, zno.50-0.90, MnO. 17-0.27, Mg margin. Sample size 50mm X 25mm X 5mm via 150'" '1000. Sandpaper was polished in turn, rinsed with tap water and scrubbed with acetone, and anodized. The power supply for anodic oxidation is the domestic WYK DC voltage and current stabilizing power supply, and the structure of the electrolytic cell used is shown in Figure 1. In order to ensure the current distribution in the anodic oxidation process is more uniform, a stainless steel ring with a diameter of 12C: is used as the cathode. At the same time, in order to ensure that all the components in the electrolyte are fully mixed, an agitator is installed in the electrolytic cell and holes are cut on the cathode ring. After anodic oxidation, the samples were rinsed with tap water and distilled water successively, dried with hot air and then placed in a dryer for testing. The medium was 5%NaC1 solution, the Angle between the test surface and the vertical direction of the sample was 20, and the other surfaces of the sample were sealed and protected by adhesive tape and epoxy resin except the test surface. The electrolytes used in the above experiments are all analytical pure reagents, and the electrolyte is prepared with distilled water.

The wear resistance of the film layer was tested by sliding wear test using Klaxon EM5CBI-W3 wear tester made in Britain. The bonding strength of film layer and matrix metal was evaluated by the method of combining grid test and tape test. That is, on the anodized film of L Omm X 10mm, 100 small squares of uniform size are marked with a sharp blade with a spacing of 1mm (the depth of the scratch is controlled to ensure the exposure of the substrate metal under the film). After counting the number of small squares (NL) of the film falling off, transparent tape with a width of 24mm is affixed to the delimited area of the film. Push and roll the tape with 1500g steel block for 5 times to ensure the close combination between the tape and the film. After that, lift the tape with a force perpendicular to the film surface immediately, and count the number of small squares n2 that the film falls off again. The rating method is as follows: using 100 system, the film binding force fraction G=100-(N1 + N2).

Domestic DWH-A2 non-destructive eddy current thickness gauge was used to measure film thickness. The surface and section morphology of anodic oxide film were observed by XL-30FeG scanning electron microscope.