Regenerative Technology and Effect of CaO/(NH₄)₂CO₃ Double Precipitation on Composition of Electroless Plating Ni-P Discard Solution

In order to lengthen the plating bath service life,the regenerative technology and effect of double precipitation of CaO/(NH4)2CO3 on the composition of the electroless plating Ni-P discard solution were studied by methods of ultraviolet spectrophotometry and chemical analysis.The elimination rate of the phosphorous and sulfate salt could reach 95% and 57%,when ［Ca2+］/［HPO2+３］=1.1,processing time 3.5 h and ≤85 ℃.The loss rate of nickel salt was less than 10% and phosphoric salt changed hardly.The loss amount of complexing agent was between 46%~50%.The main composition of eletroless Ni-P solution was hardly changed after getting rid of the remaining calcium ion by using (NH4)2CO3 and active carbon adsorption.The rate of depositon,hardness and porosity of the coating were close to those with a new bath.