摘要：本文利用化学镀在镁合金表面制备镀层。分别研究前处理中的助剂种类、浓度、时间对酸洗活化层耐腐蚀性能的影响，化学镀液的温度、pH、时间对镀层质量和厚度的影响。利用能谱仪(EDAX)、X射线衍射仪(XRD)、扫描电镜(SEM)、电化学方法等对镀层进行了表征。研究结果表明，酸洗活化的较佳工艺条件为：助剂选用硝酸钆、浓度为10mmol/L、酸洗时间为20s，该条件下制备的酸洗活化层用高锰酸钾点滴试验5min不褪色。化学镀的较佳工艺条件为：镀液主盐选用碱式碳酸镍、镀液温度80℃，pH=7、施镀时间为2h，该条件下制备的镀层质量为0.2109g，镀层厚度为33.41µm。EDAX结果表明，酸洗活化层中Mg、O、P、Gd、B元素含量依次为41.08%、47.32%、9.38%、1.72%、0.51%，镀层表面有Ni、P元素，属于Ni-P镀层，磷含量达到30.88%。XRD结果表明，酸洗活化层部分覆盖镁合金表面，镀层为Ni8P3六方晶型结构。SEM结果表明，酸洗活化层有许多裂纹，呈不规则的鳞片状，Ni-P镀层为胞状结节结构紧密排列。塔菲尔曲线表明，酸洗活化层、Ni-P镀层的自腐蚀电位与镁合金表面的相比分别正移了0.164 V、0.827 V，酸洗活化层的耐腐蚀性能比镁合金好，Ni-P镀层的耐腐蚀性能比酸洗活化层更好。

关键词：  镁合金；酸洗活化；稀土；化学镀

Study on the process of electroless nickel plating on magnesium alloy

Abstract: Electroless plating is applied on the surface of magnesium alloy. The effects of the type, concentration and time of the additives on the corrosion resistance of the activated layer of the acid pickling were studied. The effects of the temperature, pH and time of the electroless plating bath on the quality and thickness of the coating were investigated. The coatings were characterized by energy dispersive spectrometer (EDAX), X ray diffractometer (XRD), scanning electron microscope (SEM) and electrochemical method. The results show that the better process conditions for the activation of acid washing are as follows: the additive is gadolinium nitrate, the concentration is 10mmol/L, and the acid washing time is 20s. The activated layer of acid washing under this condition is not fading by the Potassium Permanganate drop test 5min. The best process of electroless plating is that the main salt of the bath is nickel carbonate, the temperature of the plating bath is 80, pH=7, and the plating time is 2H. The coating quality is 0.2109g and the thickness of the coating is 33.41 m. EDAX results show that the content of Mg, O, P, Gd and B in the activated layer of acid washing is 41.08%, 47.32%, 9.38%, 1.72%, 0.51%, and the surface of the coating has Ni and P elements, which belong to the Ni-P coating and the phosphorus content is 30.88%. The results of XRD showed that the surface of the magnesium alloy was partially covered by acid pickling active layer, and the coating was Ni8P3 six square crystal structure. SEM results show that there are many cracks in the activation layer of acid pickling, irregular scales, and Ni-P deposits are closely arranged in cellular nodules. The Tafel curve shows that the self corrosion potential of the activated layer and Ni-P coating is 0.164 V and 0.827 V respectively, and the corrosion resistance of the activated layer is better than that of the magnesium alloy, and the corrosion resistance of the Ni-P coating is better than that of the acid washing activation layer.

Key words: Magnesium alloy; Acid washing activation; Rare earth ; Electroless plating

目录

1 前言 1

1.1 引言 1

1.2 镁合金及稀土镁合金 1

1.3 镁合金表面处理技术 2

1.3.1 化学转化处理 2

1.3.2 阳极氧化 2

1.3.3 微弧氧化 3

1.3.4 激光表面处理 3

1.3.5 化学镀 3

1.4 镁合金化学镀镍技术的研究现状 3

1.4.1 化学镀镍的机理 4

1.4.2 化学镀镍的分类 5

1.4.3 化学镀镍前处理 5