摘要:化学镀在生活的各个方面都得到了广泛认可和应用，是一种广受人们欢迎的表面镀层工艺，而化学镀Ni-P合金镀层更是得到人们的青睐。在化学镀Ni-P合金工艺中，络合剂的选择、镀液的配方以及控制工艺非常重要，镀层的结构性能与形貌特征直接决定镀层的实用价值。本实验以化学镀Ni-P合金工艺参数展开实验，着重研究了柠檬酸钠、丙酸、酒石酸和苹果酸络合剂，得知柠檬酸钠络合剂能提高镀液的稳定性和络合效果，其镀液的最佳配方以及最佳控制工艺为：硫酸镍30g/L、乙酸钠20g/L、次亚磷酸钠30g/L、柠檬酸钠12g/L、四硼酸钠2g/L、硫脲1mg/L。化学镀前需严格按照要求对粗样进行预处理，用乳酸调节pH=4.5～5.5，温度控制在T=80～90℃，次亚磷酸钠分开溶解后再加入镀液。利用金相观察、SEM形貌分析、硬度检测、极化曲线分析、阻抗分析、孔隙率分析以及EDS分析得出化学镀Ni-P合金镀层外表形貌美观、致密且平整、硬度较高、抗腐蚀能力强，其镀层中主要元素为Ni和P，Ni的重量含量为90.47%，原子含量为83.36%，P的重量含量为9.53%，原子含量为16.64%。运用密度泛函理论（DFT）方法研究了柠檬酸、乳酸与Ni离子络合稳定能。试图解释为什么柠檬酸相对于乳酸，对于Ni离子是一种络合稳定性高的络合剂。研究结果表明，在镍离子中，柠檬酸络合最稳定，乳酸络合其次，镍离子水溶液稳定性最小。这个结果与络合剂稳定常数相符（乳酸稳定常数2.5；柠檬酸稳定常数6.9）。关键词：络合剂；化学镀Ni-P合金；Q235钢；耐蚀性能；量子化学计算

Abstract:Chemical plating in all aspects of life have been widely recognized and applied, is a widely welcomed by the surface coating process, and chemical plating Ni-P alloy coating is making people more interested. In the electroless Ni-P alloy process, the choice of complexing agent, the formulation of the bath and the control process are very important. The structural properties and morphology of the coating directly determine the practical value of the coating.In this experiment, the process parameters of electroless Ni-P alloy were studied. The effects of sodium citrate, propionic acid, tartaric acid and malic acid complex were studied. It was found that sodium citrate complex could improve  the stability and complexation of the bath Effect, the best formula to get the bath and the best control process: 30 g/L of nickel sulfate, 20 g/L of sodium acetate, 30 g/L of sodium hypophosphite, 12 g/L of sodium citrate, 2 g/L of sodium tetraborate, 1 mg/L of thiourea. Electroless plating in accordance with the requirements of the coarse sample pretreatment, with lactic acid pH = 4.5 ~ 5.5, the temperature control in the T = 80 ~ 90 ℃, sodium hypophosphite dissolved separately after adding the bath. The results show that the electroless Ni-P alloy coating is good, compact and smooth, and the hardness is high, and the main elements in the coating are Ni and P, the weight content of Ni is 90.47%, the atomic content is 83.36%, the weight content of P is 9.53%, the atomic content is 16.64% by metallographic observation, SEM topography analysis, hardness testing, polarization curve analysis, impedance analysis, porosity analysis and EDS analysis. The stability of citric, lactic and Ni ion have been investigated by means of the density functional theory(DFT). The calculated results indicated that the citric coordination was more stable than lactic coordination. The result is consistent with the stability constant of them (lactic acid stability constant 2.5; citric acid stability constant 6.9).

Key words: Complexing agent ； Electroless Ni-P alloy ； Q235 steel ； Corrosion resistance；Quantum chemical calculation

目录

第一章绪论 1

1.1化学镀