浸镀铜前处理对铝合金表面Ni-P镀层结构与性能的影响

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

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。

Electroless Ni-P 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 Ni-P coating.Cu layer was obtained by galvanic replacementfrom adeep eutectic solventcomprising a mixture of choline chloride and ethylene glycol with CuCl_2·2H_2O as copper source,and then electroless Ni-P coating was prepared.As a comparison,the Ni-P 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,X-ray diffraction,potentiodynamic polarization and cross-cut tape tests according to ASTM D3359-93.The results show that the Ni-P coating with Cu pretreatment is characterized byhemispherical structure,and exhibits excellent corrosion resistance with a corrosion potential of-0.343 Vand a current density of 2.109×10-6 A/cm2.According a to ASTM D3359-93,the adhesion quality forthe test result can be ranked as 5B.