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采用化学镀工艺在45钢表面制备Ni-Co-Cu-P四元合金镀层,通过EDX、XRD、SEM、盐雾试验、Tafel曲线等测试方法研究镀层的成分、晶型结构和耐蚀性能。结果表明:Ni-Co-Cu-P镀层为非晶结构,其中Ni、Co、Cu的含量分别为32.66%、47.19%和15.28%(质量分数)。镀层表面均匀分布着直径240~500 nm的球状团簇,一些团簇内部存在纳米级孔隙。镀层经156 h盐雾后出现明显红色锈点,192 h后完全失效。镀层的耐蚀性能明显优于45钢基体和Ni-Co-P镀层。在1.0%H_2SO_4溶液中,镀层的自腐蚀电位和腐蚀电流密度分别为–0.26 V和19.17μA·cm-2,随着电位的升高表面出现大量微裂纹。而在3.5%NaCl(质量分数)溶液中,镀层表现出活化-钝化-过钝化的腐蚀行为,表面钝化膜逐渐被Cl~-穿透而形成针孔。
The electroless plating process was used to prepare Ni-Co-Cu-P quaternary alloy coating on the surface of 45 steel. The composition, crystal structure and corrosion resistance of the coating were studied by EDX, XRD, SEM, salt spray test and Tafel curve. The results show that the Ni-Co-Cu-P coating is amorphous, in which Ni, Co and Cu contents are 32.66%, 47.19% and 15.28% respectively. The surface of the coating is uniformly distributed with spherical clusters with diameter of 240-500 nm, and some clusters have nano-scale pores inside. After 156 h salt spray, the coating showed obvious red rust, which completely failed after 192 h. The corrosion resistance of the coating is obviously better than 45 steel substrate and Ni-Co-P coating. In 1.0% H 2 SO 4 solution, the self-corrosion potential and corrosion current density of the coatings were -0.26 V and 19.17 μA · cm-2, respectively. A large number of micro-cracks appeared on the surface with the increase of potential. In 3.5% NaCl (mass fraction) solution, the coating showed the activation - passivation - passivation corrosion behavior, the surface passivation film was gradually penetrated by Cl ~ - to form a pinhole.