ã€China Aluminum Network】 Zinc electroplating on magnesium alloys can greatly improve the corrosion resistance of magnesium alloy surface, and it has the advantages of beautiful appearance, high hardness, good wear resistance, etc., and has been widely used. Zinc coating can be used as the bottom layer of the subsequent coating, after passivation can also meet the requirements of protection and decoration. Compared with other kinds of plating, the cost of galvanizing is low, protection and decoration are better, and the bath is relatively stable. Domestic researchers have done a lot of research in this area. Liu Yunxi and others compared the advantages and disadvantages of zinc electroplating with different solution systems on the basis of zinc immersion. When sulphate is galvanized, it is easy to corrode the magnesium alloy substrate due to its strong acidity. Zinc galvanizing provides a coating with good compactness and good adhesion under conditions of a current density of 3.0 to 4.0 A/dm2 and a time of 20 minutes. Pyrophosphoric acid electroplating zinc under the current density of 2.0 ~ 3.0A/dm2, time 10min conditions, can get a good bonding force of the coating. The addition of additives such as phytic acid and vanillin helps to reduce the porosity of the pyrophosphate zinc plating layer. Zhou Qiuqiu et al. used a two-step electrodeposition method to deposit a metallic zinc coating on the AM60 magnesium alloy as a transition layer between the magnesium alloy substrate and the electroless nickel plating layer. The presence of a zinc intermediate layer helps to reduce the galvanic corrosion between the electroless nickel coating and the magnesium alloy substrate. Yin Jianjun et al. performed pretreatment of AZ91D magnesium alloys through appropriate etching and activation processes. Alkaline galvanizing processes were then used to obtain a uniform, dense, aesthetically pleasing zinc coating with a strong bond to the substrate. Han Xiayun also conducted research on electro-galvanizing of magnesium alloys.
The immersion zinc process is used as a pretreatment process for electroplating, and the resulting immersion zinc layer is uniform and dense, and can protect the substrate from the corrosion of the plating solution during the electroplating process, and at the same time provide good bonding force for the electroplating layer as an intermediate layer. Harbin Institute of Technology, in conjunction with researchers at the measuring plant in Weihai, Shandong Province, conducted a comparative study on the alkaline zincate electrogalvanizing process and the pyrophosphate electroplating process on the basis of the zinc leaching process.
Through the above studies, it was concluded that the zinc coating obtained from the zincate zincate zincate process is bright and has high corrosion resistance. When the thickness of the alkaline zincate zinc plating layer exceeds 10 μm, it is uniformly colored after passivation. Salt spray test more than 96h. Pyrophosphate zinc plating process leveling ability is good, crystal coating is delicate. The pyrophosphate zinc plating layer is used as the bottom layer, and the alkaline zincate thickening and galvanizing can effectively improve the gloss and corrosion resistance of the zinc plating layer, and at the same time reduce the cost.
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