采用AZ31 镁合金为基体材料, 经机械抛光、碱洗、化学转化等工序, 在其表面形成致密的复合转化膜. 采用扫描电子显微镜(scanning electron microscope, SEM) 观察表面形貌和能谱分析(energy dispersive analysis, EDS) 转化膜的成分, 通过Tafel 曲线和点滴腐蚀试验评定转化膜的耐蚀性. 结果表明, 转化膜由镁、铝、氧、磷、锌及少量的锰和锆元素组成, 转化膜结合力和耐蚀性较好.
A new chromium-free conversion coating on magnesium alloy was prepared. A cast magnesium alloy AZ31 series was used as the raw material. Compact chemical conversion coating was formed on the surface after mechanical polishing, alkaline washing, and chemical conversion. Surface morphology and composition of the coating were analyzed with a scanning electronic microscopy (SEM). Energy dispersive analysis (EDS) Tafel curves and drop corrosion test were used to evaluate the corrosion resistance of the conversion coating. The results show that compositions of coating are magnesium aluminum, oxygen, phosphorus, zinc, manganese and zirconium, and the coating has good adhesion and corrosion resistance.
[1] Gao H F, Tan H Q, Li J, et al. Synergistic effect of cerium conversion coating and phytic acid conversion coating on AZ31B magnesium alloy [J]. Surface and Coatings Technology, 2012, 212(11): 32-36.
[2] 董春艳, 安成强, 郝建军, 等. 镁合金无铬化学转化膜的研究进展[J]. 电镀与精饰, 2011, 33(3): 17-21.
[3] 张华, 姚广春, 刘宜汉. 镁合金无铬化学转化膜的研究进展[J]. 材料导报, 2007, 21(3): 77-80.
[4] Yong Z Y, Zhu J, Qiu C, et al. Molybdate/phosphate composite conversion coating on magnesium alloy surface for corrosion protection [J]. Applied Surface Science, 2008, 255(5): 1672-1680.
[5] Chong K Z, Shih T. Conversion-coating treatment for magnesium alloys by a permanganate–phosphate solution [J]. Materials Chemistry and Physics, 2002,
80(1): 191-200.
[6] Liu J, Guo Y, Huang W, Phytic acid conversion coatings of magnesium [J]. Chinese Journal of Chemistry, 2010, 28(4): 639-646.
[7] Zeng R C, Lan Z D, Kong L H, et al. Characterization of calcium-modified zinc phosphate conversion coatings and their influences on corrosion resistance of AZ31 alloy [J]. Surface and Coatings Technology, 2011, 205(11): 3347-3355.
[8] Takai M, Takaya M. Influence of conversion coating on magnesium and aluminum alloys by adhesion method [J]. Materials Transactions, 2008, 49(5): 1065-1070.
[9] Abdel S H, Farahat M. Chrome-free zirconiabased protective coatings for magnesium alloys [J]. Suface and Coatings Technology, 2010, 204(16/17): 2834-2840.
[10] 李玲莉, 杨雨云, 赵刚, 等. 镁合金表面钇盐化学转化膜的制备与表征[J]. 哈尔滨工程大学学报, 2012, 33(12): 1-6.
[11] 杨晓冰, 郭瑞光, 兰力强. 国内外镁合金无铬转化技术研究规模及进展[J]. 材料保护, 2011, 44(9): 48-50; 68; 93.
[12] 崔学军, 周吉学, 王修春. 镁合金AZ31 表面无铬磷酸盐转化膜的制备、结构及性能[J]. 中国腐蚀与防护学报, 2012, 33(1): 13-17.
[13] 姜丽丽, 郭瑞光. AZ31B镁合金无铬转化膜的制备及性能[J]. 材料保护, 2012, 45(7): 31-33; 74-75.
[14] Gedvidas B, Alma R, Virginija B, et al. Formation of conversion coatings on magnesium alloy AZ31 in solutions containing nicotinic acid [J]. Materials
Science-Medziagotyra, 2012, 18(2): 123-127.
[15] Lin C S, Fang S K. Formation of cerium conversion coatings on AZ31 magnesium alloys [J]. Journal of the Electrochemical Society, 2005, 152(2): 54-59.
[16] 高阳, 代明江, 向兴华, 等. AZ91D镁合金磷酸盐转化膜的制备及性能[J]. 电镀与涂饰, 2010, 29(10): 32-36.
[17] 耿淑华, 黄红艳, 许源荣, 等. 双向脉冲电沉积法在钕铁硼永磁体表面制备铁-镍-钴合金[J]. 电镀与涂饰, 2012(10): 11-14.
