| HAO Jian-jun,DAI Zhao-yi,WANG Xin-hui,YIN Hong-kun.Preparation of Acidic Vanadium/Zirconate Conversion Coatings on AZ91D Magnesium Alloy[J],47(4):201-206 |
| Preparation of Acidic Vanadium/Zirconate Conversion Coatings on AZ91D Magnesium Alloy |
| Received:October 27, 2017 Revised:April 20, 2018 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2018.04.030 |
| KeyWord:magnesium alloy vanadate/zirconate acid system chemical conversion coatings corrosion resistance sodium metavanadate hexafluorozirconic acid |
| Author | Institution |
| HAO Jian-jun |
Shenyang Ligong University, Shenyang , China |
| DAI Zhao-yi |
Shenyang Ligong University, Shenyang , China |
| WANG Xin-hui |
Shenyang Ligong University, Shenyang , China |
| YIN Hong-kun |
Shenyang Ligong University, Shenyang , China |
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| Abstract: |
| The work aims to improve corrosion resistance of AZ91D magnesium alloy. A new type of acidic vanadium/zirconate system was used to prepare chemical conversion coatings on the surface of magnesium alloy, and optimum technological conditions of conversion coatings were studied. The acid vanadate/zirconate conversion coatings were prepared on the surface of magnesium alloy by using sodium vanadate, hexafluorozirconic acid and ammonium fluoride. Electrochemical workstation was applied to evaluate electrochemical ac impedance curve (EIS), Tafel polarization curve, corrosion current and polarization resistance of the conversion coatings. The main constituents of the coatings were analyzed with X-ray diffractometer (XRD). Microstructure of the conversion coatings was analyzed with scanning electron microscope (SEM). The vanadium/zirconate conversion coatings were successfully prepared on the surface of magnesium alloy. The film layers were grayish, dense and smooth, which made salt fog resistance duration of magnesium alloy increase from 0.2 h to 4.5 h, corrosion current decrease to 1.883105 A and polarization resistance increase to 2200 Ω. The main constituents of vanadium/zirconate conversion coatings were Zr(OH)4, V2O5, VO2 and MgF2. Meanwhile, the microstructure of vanadium/zirconate conversion coatings showed that the conversion coatings were composed of two layers of films, the bottom layer was polygonal film layer, and top layer was granular compound. The acidic vanadate/zirconate conversion coatings can improve corrosion resistance of AZ91D magnesium alloy sucessfully. |
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