基于三元复合络合剂的高磷Ni-P化学镀

针对单一络合剂难以兼顾镀液稳定性、镀速和镀层质量等多重要求,现有复合络合剂或成本过高、或工艺稳定性欠佳等问题,采用柠檬酸钠-乳酸-乙酸钠三元复合络合剂,借助增重法、扫描电子显微镜(SEM)、能谱仪(EDS)和材料耐蚀性快速检测专利技术,系统研究了络合剂及还原剂用量、镀液初始pH值及施镀温度对化学镀Ni-P施镀效果的影响,探明镀速、镀层硬度及其P质量分数、镀层腐蚀防护性能随工艺参数的变化规律。结果表明:利用基于三元复合络合剂的镀液,不仅可获得P质量分数最高为18.41%的高磷Ni-P镀层,而且工艺稳定性优异。在适宜的镀液初始pH值区间(4.0~5.5),镀层P质量分数受其它工艺参数的影响甚微,能始终稳定在11.12%~14.52%的高位。典型试样SEM分析表明:镀层表面平整、均匀,结构致密,镀层与基体结合紧密且厚度分布均匀。

Electroless Plating of Ni-P Alloys with High P Content Based on Ternary Compound Complexing Agents

Single complexing agents cannot meet multiple demands including stability of bath, plating rate and quality of coating. Existing compound complexing agents are either too expensive or unsatisfactory in process stability. To solve these problems, electroless plating (EP) based on ternary compound complexing agent consisting of sodium citrate, lactic acid and sodium acetate was studied. Effects of complexing agents, reducing agent, initial bath pH and plating temperature on EP were systematically investigated using mass gain method, SEM, EDS, and proprietary rapid test method of corrosion resistance for materials. Relationships between process parameters and plating rate, microhardness of coatings and their P content, corrosion protection were discovered. The results show that using the developed compound complexing agent, not only the NiP coatings with P content up to 18.41% can be obtained but also the EP process is very stable. In a suitable initial bath pH range of 4.05.5, the P contents of EP coatings are slightly affected by other process parameters. They can remain stable from 11.12% to 14.52%. SEM observation reveals that the obtained typical EP coating is smooth, even and compact in surface micromorphology with uniform thickness distribution and excellent adhesion.