铝及铝合金全光亮化学镀镍磷合金工艺优选

Technology for Electroless Bright Nickel-Phosphorous Alloy Plating on Aluminum and Aluminum Alloy

化学镀镍前的预处理对镀层性能非常重要，目前常用的预处理方法存在许多缺陷。为此，通过对各种预处理工艺的筛选，确定了适用于铝合金化学镀镍磷合金的条件预处理工艺并预镀中间层，然后在传统化学镀镍磷镀液中加入镀镍中间体和无机盐，组合出了一种新的全光亮化学镀镍磷合金工艺，探讨了镀液主要成分和工艺条件对沉积速度、镀层耐蚀性和外观质量的影响，并考察了镀液和镀层的有关性能。获得的最佳化学镀工艺参数为：25～35g／L硫酸镍，25～40g／L次磷酸钠，15～25mL／L乳酸，8～12g／L柠檬酸钠，15g／L乙酸钠，10mg／L2．乙基已基硫酸钠，0．4g／L糖精，5—10mg／LPPS，5—10mg／LDEP，40—50mg／L无机盐；pH值4．4～4．8，温度80～90℃。用该工艺所得镍磷合金层结晶细致、达到全光亮，与铝合金基体结合力好，耐蚀性好，适用于铝及铝合金装饰性化学镀镍磷合金，拓展了铝及铝合金的应用范围。

Pretreatment technology suitable for electroless Ni-P alloy plating on Al alloy was selected.A novel process of all bright electroless Ni-P alloy plating was established by adding Ni plating intermediate and inorganic salts into conventional electroless Ni-P plating bath.The effects of composition of the plating bath and plating conditions on the deposition rate,corrosion resistance and appearance of the coating were analyzed.It was found that the optimized plating bath consisted of 25~35 g/L nickel sulfate,25~40 g/L sodium hypophosphite,15~25 mL/L lactic acid,8~12 g/L sodium citrate,15 g/L sodium acetate,10 mg/L 2-ethyl hexyl sodium sulfate,0.4 g/L saccharin,5~10 mg/L PPS,5~10 mg/L DEP and 40~50 mg/L inorganic salt.The optimized pH value and temperature were determined as 4.4～4.8 and 80~90 ℃ respectively.The Ni-P alloy coating obtained under the optimized plating condition was fine and bright,and had good adhesion to Al substrate and good corrosion resistance,showing promising application in decoration of Al and Al alloy.