Ni-Cu-P合金镀层表面稀土复合转化膜的性能

Performance of Rare-Earth Composite Conversion Films on Ni-Cu-P Coating

Ni-Cu-P三元合金镀层在烟气冷凝液中具有较好的耐蚀性能,但仍不能完全满足要求,还需做进一步的防腐蚀处理。稀土转化膜能有效地改善Ni-Cu-P合金镀层的耐蚀性能,为提高单层稀土转化膜的性能,在稀土转化液中添加苯并三氮唑(BTA)与稀土元素复合成膜。采用扫描电子显微镜、电子能谱仪和傅立叶变换红外光谱仪分析转化膜的表面形貌及化学成分,采用极化曲线和交流阻抗分析转化膜的耐蚀性能。结果表明:单层硝酸铈转化膜表面存在微裂纹,BTA可与稀土元素复合成膜,优化膜层形貌,抑制微裂纹的形成,使膜层更致密;复合转化膜的电荷转移电阻较单层转化膜的大,腐蚀电流密度较小,与单层转化膜和合金镀层相比,复合转化膜的腐蚀电流密度分别降低约40%和90%,耐蚀性能最佳。

Benzotriazole(BTA) was added into rare earth conversion solution to form composite films with rare earth elements.The surface morphology and chemical composition of rare-earth conversion films on Ni-Cu-P coating were investigated by using scanning electron microscope,energy dispersive X-ray spectroscopy,and inductively coupled plasma atomic emission spectrometry,and the corrosion resistance was studied by polarization curve(PC) and electrochemical impedance spectroscopy(EIS).Results showed that the single-layer cerous nitrate film had some surface microcracks,while the BTA could be combined with rare earth elements into the film to optimize the morphology of the film and inhibit the formation of micro cracks,making the film surface denser and more uniform.In addition,the composite conversion film possessed larger charge transfer resistance and smaller corrosion current density than single-layer film.Compared with single-layer film and alloy coating,the corrosion current density reduced about 40%and 90%respectively,exhibiting the best corrosion resistance.