Abstract: In this study, we sought to find out the alterations in morphology, composition, porosity, adhesion and corrosion resistance of chromium-free zinc-aluminum coatings caused by variation of sodium molybdate (inhibitor) content. Specifically, SEM and EDS was adopted to characterize the morphology, porosity and composition of the coatings. The adhesion of the coatings was evaluated by adhesion tester. The corrosion resis-tance of the coatings were analyzed based on polarization curves and electrochemical impedance spectroscopy. When 1.3wt%~2.6wt% sodium molybdate was contained, the coatings were glossy and smooth with silver-gray metallic luster in appearance. Meanwhile, the coatings were complete and compact with low porosity according to the microscopic observation, and the sheet-like zinc-aluminum powders stacked layer by la-yer, forming an effective physical shielding. When the content of sodium molybdate ranged from 1.3wt% to 2.2wt%, the adhesion of coatings leveled ISO-1. While higher sodium molybdate content would do harm to the adhesion of the coatings. As the sodium molybdate content increased, the self-corrosion potential of the coatings first dropped and then went up. When the content of sodium molybdate exceeded 2.6wt%, the coating held a self-corrosion potential higher than Q235 steel matrix, and failed to provide cathodic protection for the matrix. Furthermore, the self-corrosion current of the coatings varied in the range of 9.141×10-6—1.176×10-4 A/cm2, and the Rf value (the resistance of zinc-aluminum powders surface film layer) varied in the range of 212.1—649.5 Ω·cm2. The coatings achieved the best comprehensive performance under the sodium molybdate content of 1.8wt%. In this case, the coating exhibited the minimum self-corrosion current density of only 9.141×10-6 A/cm2, and the highest Rf value of 649.5 Ω·cm2. As a result, the corrosion product film on the surface of zinc-aluminum powders was the most compact, with strong adhesion and optimal corrosion resistance.
Lonca M. Finishing, 1990, 14(9), 35.2 Malkin I, Palm B E, Ridder J A, et al. U.S. patent application, US3671331, 1972.3 Song J W, Du M. Corrosion & Protection, 2007, 28(8), 411(in Chinese).宋积文, 杜敏. 腐蚀与防护, 2007, 28(8), 411.4 Wilcox G D, Wharton J A. Transactions of the Institute of Metal Finis-hing, 1997, 75(6), 140.5 Jiang X, Guo R G, Jiang S Q. Journal of Magnesium and Alloys, 2016, 4(3), 230.6 Sun W, Zhu L Q, Li W P, et al. Journal of Materials Engineering, 2018, 46(12), 110(in Chinese).孙伟, 朱立群, 李卫平, 等. 材料工程, 2018, 46(12), 110.7 Wan B H, Fei J Y, Wang S P, et al. Materials Review A:Review Papers, 2010, 24(10), 87(in Chinese).万冰华, 费敬银, 王少鹏, 等. 材料导报:综述篇, 2010, 24(10), 87.8 Zhang X M, Liu C M, Wang J J, et al. Journal of Materials and Metallurgy, 2012, 11(1),58(in Chinese).张旭明, 刘春明, 王建军, 等. 材料与冶金学报, 2012, 11(1),58.9 Clermont F R, Creil F R, Saint Witz F R, et al. U.S. patent application, US416375, 2004.10 Zhou W J, Xu L K, Wang J, et al. Corrosion Science and Protection Technology, 2008, 20(4), 292(in Chinese).周文娟, 许立坤, 王佳, 等. 腐蚀科技与防护技术, 2008, 20(4), 292.11 Jiang Q. Research on preparation and corrosion mechanism of Zn-Al-based alloy coatings based on dacromet coating. Ph.D. Thesis, Nanjing University of Aeronautics and Astronautics, China, 2014(in Chinese).蒋穹. 基于达克罗技术的Zn-Al基合金涂层的制备及耐蚀机制研究. 博士学位论文, 南京航空航天大学, 2014.12 Liu X S, Du W W, Wang Y, et al. Materials Protection, 2017, 50(6), 61(in Chinese).刘秀生, 杜雯雯, 汪洋, 等. 材料保护, 2017, 50(6), 61.13 Liao J W, Wang G, Xie G R, et al. Electroplating & Finishing, 2017, 36(9), 478.14 Tong F. Study on chromium-free zinc-aluminum coatings enhanced by nano materials. Master’s Thesis, Nanjing University of Aeronautics and Astronautics, China, 2014(in Chinese).仝飞. 微纳米材料增强无铬锌铝涂层研究. 硕士学位论文, 南京航空航天大学, 2014.15 Sun G X. Study on properties and preparation of sliane film. Master’s Thesis, Shenyang Ligong University, China, 2012(in Chinese).孙广霞. 硅烷膜的制备及性能研究. 硕士学位论文, 沈阳理工大学, 2012.16 Xiao Y X, Jiang X H, Xiao Y D, et al. Procedia Engineering, 2012, 27, 1644.17 Matsuzaki A, Yamaji T, Yamashita M. Surface & Coatings Technology, 2003, 169, 655.18 He J B, Lu D R, Li X L, et al. Chemical Research and Application, 2002, 14(1), 81(in Chinese).何建波, 鲁道荣, 李学良, 等. 化学研究与应用, 2002, 14(1), 81.19 Liu J G, Yan C W. Surface & Coatings Technology, 2006, 200(16), 4976.20 Liu Z L, Zhang S D, Liu X Q, et al. Surface Technology, 2017, 46(8), 7(in Chinese).刘子利, 章守东, 刘希琴, 等. 表面技术, 2017, 46(8), 7.
渝公网安备50019002502923号 版权所有：《材料导报》编辑部
2020, Vol. 34 
