化学镀Ni-W-P薄膜的制备及其耐蚀性能的研究

目的 制备Ni-W-P合金薄膜并研究其耐蚀性.方法 在碱性镀液(pH=11)中,以次亚磷酸钠为还原剂,柠檬酸钠为络合剂,以铜锌合金为基材,采用化学镀制备Ni-W-P薄膜.通过X射线荧光仪、SEM、电化学极化曲线等方法 ,研究还原剂次亚磷酸钠浓度、络合剂柠檬酸钠浓度以及反应时间对薄膜厚度、表面形貌和耐蚀性的影响.结果 固定其他参数不变的条件下,在还原剂浓度为0.2 mol/L及络合剂浓度为0.26 mol/L时薄膜厚度最大,分别为0.2975、0.1978μm.随着次亚磷酸钠浓度的增大,Ni-W-P薄膜表面致密度增加,孔隙率减少.当次亚磷酸钠的浓度为0.1 mol/L时,薄膜表面的颗粒较细小,孔隙较多;当次亚磷酸钠的浓度为0.4 mol/L时,薄膜表面的孔隙明显减少,表面更加均匀且致密度变好;络合剂和还原剂的改变对薄膜腐蚀电位没有明显影响,腐蚀电流密度在还原剂浓度为0.4 mol/L、络合剂浓度为0.28 mol/L时达到最小,分别为2.38×10-6、2.23×10-6 A/cm2;随着络合剂和还原剂浓度的增大,薄膜表面趋于致密;随着反应时间的增加,膜层厚度明显增大,腐蚀电流密度随着时间的增加而减小,化学镀4 h薄膜腐蚀电流密度最小,为1.679×10-6 A/cm2.Ni-W-P薄膜厚度可达到4.14μm.结论 还原剂浓度为0.4 mol/L,络合剂浓度为0.28 mol/L时,薄膜的耐蚀性最好,反应时间的延长有利于薄膜耐蚀性能的优化.

Preparation and Corrosion Resistance of Electroless Plating Ni-W-P Alloy

Objective Ni-W-P coatings were prepared on copper-zinc alloy substrates by electroless deposition to study the anti-corrosion performance. Methods Ni-W-P coatings were prepared by electroless deposition using hypophosphite as reducing agent and sodium citrate as complexing agent in the alkaline solution (pH=11). The investigation was focused on the effects of chemical agents and reaction time on the performance of Ni-W-P coatings. The thickness, surface morphology and corrosion behavior of the coatings were analyzed by X-ray fluorescence analyzer, scanning electron microscopy ( SEM) and electrochemical workstation, re-spectively. Results With the increasing concentrations of reducing agent (0. 1~0. 4 mol/L) and complexing agent (0. 18~0. 28 mol/L), the thickness of the coatings reached the maximum. Especially, Ni-W-P coatings with thickness of 0. 2975 μm and 0. 1978 μm could be obtained respectively in the conditions of 0. 2 mol/L reducing agent and 0. 26 mol/L complexing agent. With the increasing concentration of reducing agent, the surface density increased while the porosity decreased. When the concentration of hypophosphite was 0. 1 mol/L, coatings with smaller particles and porous surface could be obtained. However, dense and uni-form coatings could be detected at the condition of 0. 4 mol/L hypophosphite. Corrosion current density reached the minimum when the reducing agent concentration was 0. 4 mol/L, and the complexing agent concentration was 0. 28 mol/L, which corresponded to 2. 38×10-6 A/cm2 and 2. 23×10-6 A/cm2, respectively. With the increasing concentrations of reducing agent and complexing a-gent, more compact coatings could be prepared. Moreover, along with the increasing reaction time, coating thickness changed sig-nificantly and the corrosion current density decreased. The corrosion current density reached the minimum and Ni-W-P with a thickness of 4. 14 μm could be prepared when the reaction time was 4 hours. Conclusion The coatings with the best corrosion re-sistance were obtained with 0. 4 mol/L of reducing agent and 0. 28 mol/L of complexing agent. In addition, longer reaction time helped to optimize the corrosion resistance of the coatings.