Effect of Tiangang Light Stabilizer on Medium-Temperature Electroless Ni–P Alloy Plating

Effect of Tiangang Light Stabilizer on Medium-Temperature Electroless Ni–P Alloy Plating

Using plating bath stability, deposition rate, coating phosphorus content and gloss as evaluation indicators, the effects of copper sulphate, ceric sulphate and thiourea each used as Tiangang light stabilizer on medium-temperature electroless nickel plating on 45 steel were studied. The basic bath formula and process conditions were: NaH2PO2·H2O 28 g/L, NiSO4·6H2O 26 g/L, C6H8O7·H2O 12 g/L, CH3COONa·3H2O 15 g/L, sodium dodecyl sulphonate (SDS) 10 mg/L, succinic acid 3 g/L, pH 5.2 ± 0.2, temperature (75 ± 2) °C, time 1 h. Using copper sulphate as the light stabilizer gave the best coating gloss but slower deposition rate; using thiourea as the stabilizer gave the best bath stability and fastest deposition rate but lower coating gloss; using ceric sulphate as the stabilizer gave poor electroless nickel plating results. Combining 6 mg/L CuSO4·5H2O with 2 mg/L thiourea gave the best bath stability, a deposition rate of 15.72 μm/h, and a medium-phosphorus electroless nickel coating with gloss 171.3 Gs, smooth surface and fine crystallisation.