| ZHU Ding,ZHANG Xiao-bo.Corrosion Resistance of Graphite-containing Micro-arc Oxidation Coating on GZ91K Magnesium Alloy[J],49(7):53-59 |
| Corrosion Resistance of Graphite-containing Micro-arc Oxidation Coating on GZ91K Magnesium Alloy |
| Received:June 15, 2020 Revised:July 20, 2020 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2020.07.007 |
| KeyWord:magnesium alloy, graphite, micro-arc oxidation, corrosion resistance, surface treatment |
| Author | Institution |
| ZHU Ding |
1.School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing , China;2.Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing , China |
| ZHANG Xiao-bo |
1.School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing , China;2.Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing , China |
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| Abstract: |
| The corrosion resistance of the Mg-9Gd-1Zn-0.4Zr (GZ91K) magnesium alloy micro-arc oxidation (MAO) coatings was improved by adding graphite into the electrolyte. In this work, the MAO coating with and without graphite was prepared on the surface of GZ91K magnesium alloy. The morphology, composition, phase and corrosion resistance of the coatings were studied by means of SEM, EDS, XRD, electrochemical workstation and immersion test. It is found that the coating with graphite is denser and the pore diameter becomes smaller than that without graphite. The coating with graphite is mainly composed of Mg, O, C, Si, P, Gd. Compared with the coating without graphite, the composition of the coating has little change except for C. The phases of the coatings with and without graphite are mainly composed of MgO and Mg2SiO4. With the increase of the graphite concentration in the electrolyte, the corrosion resistance of the coating is improved apparently. The corrosion current density of the sample prepared by adding 5 g/L graphite is only 9.8×10–9 A/cm2, indicating that the corrosion resistance of this sample is 500 times higher than that of the sample without graphite. The simulated body fluid immersion experiment also showed that the higher the graphite content, the lower the hydrogen evolution, and the lowest hydrogen evolution was obtained by adding 5 g/L graphite. In the range of 0~5 g/L, with increasing graphite concentration, the graphite particles could easily block and cut off some holes in the film and prevent the corrosive liquid from contacting with the matrix, and thus it significantly improves the corrosion resistance of the magnesium alloy. |
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