柠檬酸对1060铝合金化学镀Ni-W-P镀层性能的影响

Influences of the citric acid on the properties of the electroless plating Ni-W-P coating on the 1060 aluminum alloy

为提高1060铝合金的耐腐蚀性能和耐磨性能,采用电化学技术、SEM和XRD等方法,研究了柠檬酸对1060铝合金化学镀Ni-W-P镀液的沉积速率、镀层的孔隙率、腐蚀电位、交流阻抗、维氏硬度、形貌等的影响。结果表明,添加柠檬酸,镀液沉积速率有所降低,但是,Ni-W-P镀层的表面平滑光亮,结合力良好,耐蚀性提高。当柠檬酸含量为25 g/L时,镀层的点滴液变色时间最长,为605 s,镀层的孔隙率为0,腐蚀电流密度最小(2.95μA/cm^2),腐蚀电位最大,为-0.384 V,比1060铝合金的正移0.889 V,腐蚀倾向变小。镀层呈典型的花椰菜包状物结构,添加柠檬酸之后,包状物细化,镀层组织结构更紧密均匀,无孔隙,镀层磷含量提高,使镀层由非晶态和微晶构成的混晶结构向非晶态转变,是其耐蚀性高的重要原因,提高钨含量使镀层硬度增加,为174 HV,是1060铝合金基体的4倍。

To increase the corrosion resistance and wear-resisting property of 1060 alumi- num alloy, the investigation was made on the influence of the citric acid on the deposition rate, porosity, corrosion potential, electrochemical impedance spectroscopy （ EIS ）, webster hardness and morphology of the electroless plating Ni-W-P coating on 1060 aluminum alloy surface by the electrochemical methods, SEM, and XRD, etc. The results show that as the cit- ric acid is added into plating bath, the deposition rate decreases, the surface becomes smooth and bright, the two parts bond well with each other, and the corrosion resistance is increased. As 25 g/L citric acid is added, the discoloration time is increased to 605 s, the porosity is 0, and the corrosion current reaches the minimum 2.95 ~A/cm2. At this time, the corrosion potential reaches the maximum -0.384 V,0. 889 V positive shift than that of the 1060 alumi- num alloy, and the corrosion tendency becomes smaller. The original broccoli structure is more refined and compact, uniform and no-porous, and the P and W content is increased,when the alloy is added with the citric acid. The increase of P content leads to the transition from the mixture of amorphous and microcrystalline to the amorphous state, which is an im- portant reason of the high corrosion resistance. The increase of W content leads to the higher webster hardness of the coating （ 174 HV） ,which is 4 times of the 1060 aluminum alloy.