铝合金电解着色用镍板失效原因分析

Analysis on the causes of early failure of nickel plate for electrolytic coloring of aluminum alloys

铝合金工件的单镍盐着色多采用镍板作为对电极,控制镍板溶解均匀性对保证槽液稳定性和铝合金工件着色质量而言至关重要。采用扫描电子显微镜、能谱仪和金相显微镜对一批在单镍盐着色过程中早期失效的镍板进行分析。结果表明,镍板晶界碳、硅的富集造成镍板发生了晶间腐蚀。镍板的晶间腐蚀会加速镍板的溶解,严重时导致晶粒脱落,还会使晶界的碳、硅等杂质脱出。这些不仅造成镍板的早期失效,而且会污染槽液,影响铝合金的着色质量。建议严格控制镍板中碳、硅等杂质含量,适当调整热处理工艺,避免碳、硅等杂质元素析出,以延长镍板的使用寿命。

Nickel plate is usually used as a counterelectrode in electrolytic coloring of aluminum alloys in abath containing single nickel salt. The control of thedissolution uniformity of nickel plate is important formaintaining bath stability and coloring quality. A batch ofnickel plates failed early in single-nickel salt electrolyticcoloring was analyzed by scanning electron microscopy,energy-dispersive X-ray spectroscopy, and metalloscopy.The results showed that intergranular corrosion occurred dueto the enrichment of carbon and silicon on crystal boundary,resulting in an accelerated dissolution of nickel plate, fall-offof grains, and segregation of carbon and silicon impurities.The early failure of nickel plate not only contaminates thebath, but also affects the coloring effect. It is suggested thatthe contents of carbon and silicon in nickel plate should becontrolled strictly and the heat treatment process be adjustedto extend the service life of nickel plate.