双脉冲电镀非晶态Ni-P工艺对镀层性能的影响

Effect of Pulse Reverse Electroplating Technology on the Properties of Amorphous Ni-P Alloy Coating

双脉冲电镀制备的镀层性能优异,而目前双脉冲电镀非晶态Ni-P镀层鲜见报道。利用双脉冲电镀制备非晶态Ni-P合金镀层,研究了平均电流密度、正向占空比、温度、亚磷酸及柠檬酸钠浓度对镀层性能的影响。结果表明:随着平均电流密度增大,Ni-P镀层的沉积速率增加,腐蚀电位越来越负,镀层表面由平整致密变得有气孔和凸起,甚至起皮;正向占空比从30%增大至70%时,镀层的组织结构从完全非晶态转变为晶态,腐蚀电位越来越负,正向占空比为30%时,腐蚀电位最正,最不易被腐蚀;温度影响镀层的光亮度和平整度,70℃时镀层外观形貌最优,腐蚀电位最正;随亚磷酸浓度的增加,镀层外观形貌由平整致密变得有大量黑色条纹和起皮,为了得到外观形貌较好且腐蚀电位较正的镀层,亚磷酸浓度在20～30g/L之间为宜;随柠檬酸钠浓度的增加,镀层沉积速率降低,腐蚀电位变正,不易被腐蚀。

Amorphous Ni-P coatings were prepared by using pulse reverse plating. The effects of aver-age current density, duty cycle, temperature and concentration of phosphorous acid and sodium citrate on the properties of the coat-ings were studied. Results show that the depositing rate of Ni-P coatings increases with increasing average current density, and the corrosion potential becomes increasingly negative therewith. The surface of the coatings changed from smooth and compact to porous with bubbles or even peelings with increasing average cur-rent density. When the duty cycle rose from 30% to 70%, the amorphous Ni-P alloy coating was transformed into crystalloid, and the corrosion potential became increasingly negative. The Ni-P coating obtained at a duty cycle of 30% had the highest positive corrosion potential and best corrosion resistance. Be-sides , temperature had an effect on the brightness and smoothness of the Ni-P coatings, and the coating obtained at 70℃ had the best appearance and highest positive corrosion potential. Moreo-ver, the surface of the Ni-P coatings was transformed from smooth and compact to incorporated with a large amount of black stripes or peelings with increasing concentration of H3PO3, and the opti-mum concentration of H3 PO3 was 20 ～30 g/L. In addition, the deposition rate of the Ni-P coatings decreased with increasing concentration of sodium citrate, and the corrosion potential be-came increasingly positive therewith, corresponding to increased corrosion resistance.