浸镀铜前处理对铝合金表面Ni-P镀层结构与性能的影响

化学镀Ni-P是提高铝合金表面耐蚀耐磨性的主要方法之一,但施镀前通常要进行前处理,以去除表面氧化膜。以氯化胆碱-乙二醇低共熔体系为溶剂,CuCl2·2H2O为铜源,通过浸镀方法在铝合金表面制备铜层,再后续化学镀NiP,并与未经浸镀前处理和浸锌前处理铝合金表面的化学镀Ni-P层进行对比。利用扫描电子显微镜、X射线衍射、动电位极化及ASTM D3359-93胶带测试法研究了不同前处理方法对Ni-P镀层结构和性能的影响。结果表明:与未经浸镀前处理和浸锌前处理相比,通过浸镀铜前处理的铝合金表面得到的Ni-P镀层呈常规的胞状颗粒结构,腐蚀电位与腐蚀电流分别为-0.343V和2.109×10-6 A/cm2,耐蚀性较好;根据ASTM D3359-93标准,镀层与基底的附着性为5B。

Effects of Cu Immersion Pretreatment on the Structure and Performance of Electroless Ni-P on Al Alloys

Electroless NiP is one of key methods to improve the corrosion and wear resistance of Al alloys. However, appropriate pretreatments are usually needed before electroless plating to eliminate oxide film of NiP coating. Cu layer was obtained by galvanic replacementfrom adeep eutectic solventcomprising a mixture of choline chloride and ethylene glycol with CuCl2·2H2O as copper source, and then electroless NiP coating was prepared. As a comparison, the NiP coatings were prepared on Al alloys without immersion and Zn immersion pretreatment. The effect of different pretreatments on the structure and properties was investigated by scanning electron microscopy, Xray diffraction, potentiodynamic polarization and crosscut tape tests according to ASTM D335993. The results show that the NiP coating with Cu pretreatment is characterized byhemispherical structure, and exhibits excellent corrosion resistance with a corrosion potential of -0.343 V and a current density of 2.109×10-6A/cm2. According a to ASTM D335993, the adhesion quality forthe test result can be ranked as 5B.