1、 镁合金论文：AZ61 镁合金的磷化及阴极电泳【中文摘要】镁合金作为优质的合金结构材料,在航空航天、汽车、电子和医疗器材等行业得到广泛应用。但是镁的耐蚀性较差,制约了镁合金的应用。镁合金磷酸盐转化膜具有多孔结构、附着力好,是有机涂层的有效基底。本文采用磷化与阴极电泳涂装相结合的方法改善 AZ61镁合金的表面性能。本研究的研究方法、研究内容和结果分别叙述如下。在国内外锌系磷化研究的基础上,选取三种不同的磷化体系。通过对三种磷化体系所得磷化膜的厚度、耐碱性、表面形貌以及元素组成进行对比,选取适宜阴极电泳涂装的磷化膜。采用单因素试验,分别研究磷化液中各物质对磷化成膜的影响。研究表明：Zn(H2PO4
2、)2的浓度对磷化膜的厚度有较大影响,浓度越大,厚度越大；NaNO3对磷化过程具有良好的促进作用；硫酸羟胺是一种良好的磷化氧化促进剂,且具有用量低的优点；NaF 能够促进磷化、细化膜层。间硝基苯磺酸钠与酒石酸添加后对磷化膜的成膜有利,但是添加的浓度与成膜状况关系较小。采用正交设计的方法设计实验,正交表为(L9(34),选取四种浓度对磷化过程影响较大的物质 NaF、硫酸羟胺、ZnH2PO4、NaNO3 作为正交试验的四个因素,物质的浓度为各因素的水平。正交优化结果：NaF 浓度为 1.67 gL-1、硫酸羟胺的浓度为1.5 gL-1、ZnH2PO4 的浓度为 23.1 gL-1、NaNO3 的浓度
3、为 5 gL-1。在上述优化物质浓度下,AZ61 镁合金表面形成的磷化膜厚度适中、w 小、均匀性好、腐蚀电流密度低、耐蚀性良好。在以上工作的基础上,采用上述磷化条件的磷化膜进行阴极电泳涂装,得到外观(颜色、光亮度、均匀性)较好,厚度在 35m 左右,硬度达到2H-3H,与基体的附着力为 0级,耐蚀性较好的复合电泳涂层。采用电涡流测厚仪测量磷化膜的厚度；利用金相显微镜、扫描电镜(SEM)观察磷化膜的表面形貌；利用化学分析方法和能谱分析(EDS)分析磷化膜的成分组成；通过阳极极化曲线、电化学阻抗谱(EIS)、腐蚀失重等方法评价磷化膜的耐腐蚀性能。电泳部分采用电涡流测厚仪测量有机涂层的厚度,采用 E
4、IS测试有机涂层的耐蚀性；按国家标准规定的方法测量有机涂层的附着力、硬度和耐溶剂性。【英文摘要】As a high-quality structural material, magnesium alloys have been used in lots of fields, especially in the aerospace, automobile, electronic and medical equipment. However, the use of magnesium alloy was severely limited by its poor corrosion resistin
5、g property. Magnesium alloy phosphating conversion treatment was an effective substrate of organic coating because of its porous and binding force. In this dissertation, phosphating and cathode electrophoretic painting methods were applied to improve the surface performance of the magnesium alloys.
6、The experimental methods, main work and results were recounted as follows separately.In this dissertation, three phosphating systems were selected on the basis of investigation both at home and abroad. We select a optimum phosphating coating for cathode electrophoretic painting by comparing the thic
7、kness, weight loss in alkaline solution, surface morphology and elements of three phosphating coatings obtained in different phosphate baths.The influences of each substance in phosphate bath on phosphate coatings were researched with single factor test. The results are as follows:the concentration
8、of Zn(H2PO4)2 has an important effect on thickness of film, the film would be thicker with a higher the concentration of Zn(H2PO4)2; the concentration of NaNO3 has effects on the accelerating of the phosphate process; hydroxylamine sulfate is a good accelerator which has characteristic of low consum
9、ption; The concentration of NaF can promote the forming of phosphme film and thin crystalline grain. Tartaric acid and nitrobenzene sulfonate have important effects on the formation of phosphate coatings, but their concentrations have no effects on it.Orthogonal design was used to scheme experiment,
10、 the concentrations of four substances were chosen as four factors of orthogonal design table (L9(34). The optimum orthogonal conditions were CNaF=l.67 gL-1, Chydroxylamine sulfate=1.5 gL-1, CznH2PO4=23.1 gL-1, CNaNO3=5 gL-1. In the optimized conditions, test results showed that the phosphate coatin
11、gs formed on magnesium alloys have moderate thickness, lower corrosion weight-loss, more detailed micro-structure and more excellent corrosion resistance than the contrast phosphate coatings. Electrophoretic composite coatings were prepared on basis of optimized phosphate coatings by cathodic electr
12、ophoretic. The appearances (color, brightness, uniformity) of the electrophoretic composite coatings obtained in the optimized conditions were better than others, the thickness was 35m, hardness was 2H-3H, adhesion was on zero level and the corrosion resistance was excellent.The thickness of the pho
13、sphate coatings were measured by the eddy curreny thickness meter. The surfaces morphologies of the phosphate coatings were observed by metallographic microscope and SEM; the compositions of the phosphate coatings were analyzed by titrimetry and EDS. The corrosion resistance of the phosphate coating
14、s were assessed by anodic polarization curves measurement, electronical impedance spectra(EIS) and corrosion weight-loss test. The thickness of the organic coatings were measured by the eddy curreny thickness meter. The corrosion resistance of the organic coatings were assessed by EIS. The thickness
15、, weight loss and solvent resistance of organic coatings were tested according to the national standards.【关键词】镁合金 磷化 表面形貌 耐蚀性 阴极电泳涂装【英文关键词】Magnesium alloys Phosphating Surface morphologies Corrosion resistance Cathode electrophoretic painting【目录】AZ61 镁合金的磷化及阴极电泳 摘要 10-12 ABSTRACT 12-13 第一章 绪论 14-30
16、1.1 镁及镁合金的性质及分类 14-16 1.1.1 镁及镁合金的性质 14 1.1.2 镁合金的分类 14-16 1.2 镁及镁合金的腐蚀 16-19 1.2.1 镁及镁合金的腐蚀反应 16-17 1.2.2 负差数效应 17-18 1.2.3 镁合金腐蚀的类型 18-19 1.3 镁合金的腐蚀防护措施 19-25 1.3.1 改变合金的显微组织 19-20 1.3.2 镁合金的表面处理 20-25 1.4 本课题的研究方向 25-30 1.4.1 镁合金磷化的特点 25-27 1.4.2 镁合金阴极电泳涂装的特点 27-28 1.4.3 研究课题的提出 28-30 第二章 实验材料、工艺
17、及研究方法 30-44 2.1 实验材料、药品及仪器 30 2.1.1 基体材料 30 2.1.2 化学试剂 30 2.1.3 实验设备 30 2.2 实验方法 30-44 2.2.1 前处理工艺 30-33 2.2.2 磷化工艺 33-35 2.2.3 阴极电泳工艺 35 2.2.4 测试方法 35-44 第三章 镁合金磷化工艺研究 44-80 3.1 磷化体系的选择 44-49 3.1.1 不同体系得到的磷化膜的厚度分析 45-46 3.1.2 不同体系得到的磷化膜的耐碱性试验 46 3.1.3 不同体系得到的磷化膜的金相显微分析 46-47 3.1.4 不同体系得到的磷化膜的扫描电镜分析
18、 47-49 3.2 磷化液中各成分对磷化的影响 49-70 3.2.1 磷酸二氢锌浓度对磷化的影响 49-52 3.2.2 有机胺对磷化的影响 52-58 3.2.3 硝酸钠浓度对磷化的影响 58-62 3.2.4 氟化钠浓度对磷化的影响 62-66 3.2.5 酒石酸浓度对磷化的影响 66-68 3.2.6 间硝基苯磺酸钠浓度对磷化的影响 68-70 3.3 磷化体系优化 70-78 3.3.1 正交设计及实验结果 70-73 3.3.2 正交最佳配方的性能测试 73-78 3.4 本章小结 78-80 第四章 镁合金磷化膜上的阴极电泳涂装 80-91 4.1 复合涂层的耐溶剂性 80-8
19、1 4.2 复合涂层的交流阻抗测试 81-88 4.2.1 最佳磷化复合电泳涂层交流阻抗测试 81-82 4.2.2 对比磷化复合电泳复层交流阻抗测试 82-84 4.2.3 表调复合电泳涂层交流阻抗测试 84-85 4.2.4 镁合金电泳涂层交流阻抗测试 85-88 4.3 阴极电泳复合涂层的厚度分析 88 4.4 阴极电泳复合涂层的硬度分析 88 4.5 阴极电泳复合涂层的附着力分析 88-89 4.6 阴极电泳复合涂层的颜色分析 89 4.7 阴极电泳复合涂层的光亮度分析 89 4.8 本章小结 89-91 第五章 结论 91-93 参考文献 93-98 致谢 98-99 附录:硕士期间发表学术论文 99-100 学位论文评阅及答辩情况表 100
