The Development Of New Formula And Recycling Treatment Of Exhausted Bath For Electroless Nickel Plating

As a new means of surface protection and consolidation, EN plating has been attracting more and more and attention at home and abroad in recent years. The main principle of EN is to utilize the autocatalytic redox reaction between metal salts and reductant in the same solution to deposit amorphous nickel-phosphorus alloy in the exterior of workpiece. The technology of EN which invented by A.Brenner and G.Qiddell of American National Standards Institute since 1944 has been growing mature gradually during over 60 years. In virtue of the continuous spread of EN and the constant expand of market demand, the industry of EN developed rapidly. It is widely applied in the hi-tech field of petroleum, chemical engineering, machinery, electronics, automobile, aviation, etc because there are many remarkable advantages such as simple facility, convenient manipulation, flexible technics, symmetrical coating, high hardness, endurance, denseness and corrosion-resistant for EN. EN is considered to be one of surface treatment technology which has grown fastest nowadays.The research develop a new EN formula and optimize diverse factors of acid EN technics using Box-Behnken design of RSM for the first time. The result demonstrates that the coating deposition rate can achieve 20.27μm·h^-1 with 30.3g/L reductant sodium hypophosphite, 30.2mg/L stabilizer lead acetate and 4.5 pH value under the condition of 30g/L main salts nickel sulfate, 10.0g/L organic acid XD and 15.0ml/L lactic acid of complexing agent, 20.0g/L buffer sodium acetate, 8.0ml/L accelerator propionic acid and 85℃temperature in the bath. The experimental data generally precedes domestic similar level.The research do an in-depth study aiming the treatment technology of current exhausted EN bath from the reality of corporation and ultimately optimize the operating condition for recycling treatment by RSM in order to solve the various environmental pollution problems caused by exhausted EN bath from enterprise plating process in the existence and explore an efficient way to take full advantage of resource, reduce the industrial product cost and eliminate pollution of nickel and phosphorus. The result shows that the removal efficiency of nickel ion could approach 99.98% under the condition of 67℃temperature, 10.2 pH value and 1.1h reaction time. The remnant nickel ion concentration of treated exhausted EN which is merely 0.5145mg/L much lower than 1.0mg/L of GB requirement. Simultaneously, the removal efficiency of total phosphorus in treated exhausted EN also could reach 99.98% above and entirely fulfill eligible discharge.