Influence of sodium silicate concentration on properties of micro arc oxidation coatings formed on AZ91HP magnesium alloys |
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| Authors: | RF Zhang SF Zhang JH Xiang LH Zhang YQ Zhang SB Guo |
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| Affiliation: | 1. Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, PR China;2. School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, PR China;3. Hunan University of Science and Technology, Xiangtan 411201, PR China |
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| Abstract: | In a base solution containing 10 g/L sodium hydroxide and 12 g/L phytic acid, the influence of sodium silicate concentration on the formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on magnesium alloys was systematically studied. The results demonstrate that sodium silicate can increase the solution conductivity, decrease the final voltage and change the coating color. Amorphous magnesium silicate is detected and the silicon content in the coatings continually increases with the increasing of sodium silicate concentration. Silicate ions can simultaneously combine with magnesium and aluminum ions to develop anodic coatings, while phytic acid radicals preferentially react with magnesium ions. Sodium silicate can further improve the corrosion resistance of MAO treated magnesium and the coating shows the best corrosion resistance in the base solution with 10 g/L sodium silicate. |
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| Keywords: | Magnesium alloys Anodic coatings Electrolytes Sodium silicate |
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