摘要镁合金是应用广泛的新型金属结构材料。然而，镁合金的耐腐蚀性能差，制约了 其发展。目前，化学转化是提高镁合金耐蚀性有效的方式，包括铬酸盐转化、磷酸盐 转化、锡酸盐转化等。

本文围绕磷酸盐转化膜进行研究，并对转化膜形貌、结构、耐腐蚀性能及工艺影 响因素进行探讨。在 AZ31 镁合金磷酸盐化学转化处理工艺中，主要研究磷酸盐成分、 促进剂、溶液 pH 值的影响。采用点滴实验、正交实验和电化学实验分析各因素对转 化膜生长和耐蚀性能的影响。用配置能谱仪（EDS）的扫描电子显微镜进行表面形貌、 成分进行分析，XRD 进行膜层结构分析。结果表明磷酸盐转化膜致密，膜层主要成 分 O、P、Mn 和 Mg 元素。膜层的主要结构是晶体，成膜物是由 Mn3O4 和 Mn3（PO4） 2 组成，且 Mn3（PO4）2 占主体。AZ31 镁合金在处理溶液 Mn（H2PO4）2 40g/l，Ca（NO3）2 2。5g/l，Ca（H2PO4）2 2。5g/l，NaF 1。0g/l，有机加速剂 3。0g/l，pH 值 4。0，处 理工艺：恒温水浴 60℃，加热 40min 时成膜性能最佳，且耐蚀性优异。

实验证明磷酸盐转化膜可以提高镁合金的耐腐蚀性能，本实验优化的成膜工艺在 工业生产中有一定的应用价值。81111

毕业论文关键词： 镁合金；磷酸盐；化学转化膜；耐腐蚀

Abstract Magnesium alloys as new structural metallic materials were widely used。  However, the poor corrosion resistance of magnesium alloy restricts its development。 Currently, Chemical conversion coating is an effective method to improve the corrosion resistance  of

magnesium alloys，for example chromate, phosphate and stannate , etc。

In this paper, phosphate was used as chemical conversion treatment solution, the morphology, structure, corrosion resistance and process influence factors would be discussed。During the study of the phosphate conversion processing treatment on AZ31 magnesium  alloys,  influencing   factors  of  the  phosphate  ingredient  were    considered,

concentrating on accelerator, pH number。 Spot test， orthogonal test and  electrochemical

experiment were used to analysis the impact of various factors on growth and corrosion resistance of coatings。 The morphology and the composition of the treated specimens were analyzed by using scanning electron microscopy (SEM) equipment with the energy dispersive analysis system (EDS)。 The structural of the film was analyzed by x-ray diffraction。 The results show that the phosphate conversion coating is compact and the

composition of the coating are mainly O、P、Mn and Mg。The main structure of the film is

crystalline , the film-forming material is composed of Mn3O4 and Mn3 (PO4) 2 , and Mn3 (PO4) 2 dominant。 The best quality of the conversion coating on AZ31 magnesium alloy have gotten in the phosphate solution of treatment solution Mn（H2PO4）2  40g/l，Ca（NO3）

2  2。5g/l，Ca（H2PO4）2  2。5g/l，NaF 1。0g/l，accelerator 3。0g/l，pH number 4。0 , water bath

60 ℃, heat 40min and corrosion resistance is excellent。

Experimental results show that the phosphate conversion coating can improve the corrosion resistance of magnesium alloy。 In this study, the optimized phosphate conversion process has a certain value in industrial production。

Keywords: magnesium alloy; phosphate; chemical conversion coating; corrosion resistance

目录

第一章 绪 论 1

1。1  镁及镁合金的概述 1

1。1。1 镁及镁合金 1

1。1。2 镁及镁合金的应用