化学镀非晶态Ni-P及Ni-Sn-P镀层在弱酸性介质中耐蚀性研究

以紫铜为基体,采用化学镀制备了非晶态Ni-P,Ni-Sn-P镀层.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线能谱(EDS)等对镀层的结构、微观形貌及元素组成进行分析.通过Tafel极化曲线、电化学阻抗谱(EIS)、开路电位监测及室内加速腐蚀试验,研究两种镀层在pH=5.5,w_(NaCl)=3.5%,以及pH=5.5,wS=20%的土壤介质中的耐蚀性能.结果表明,化学镀非晶态Ni-P及Ni-Sn-P镀层的自腐蚀电流密度是裸铜的4.5%和1.2%,两种镀层在酸性腐蚀介质中具有比金属铜更好的耐蚀性,并且化学镀Ni-Sn-P镀层耐蚀性优于Ni-P镀层.两种镀层的自腐蚀电位均负于铜.

Study of the Corrosion Resistance of Eletroless Amorphous Ni-P and Ni-Sn-P Coatings in Weak Acidic Medium

Amorphous Ni-P and Ni-Sn-P coatings were prepared on pure copper substrates by electroless plating. The structure, surface morphology and composition of the as-plated coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis (EDS). The corrosion resistance behaviors of the as-plated Ni-P and Ni-Sn-P coatings were investigated by Tafel polarization, electrochemical impedance spectroscopy (EIS), open circuit potential and accelerating corrosion indoors in wNaCl=3.5% solution at pH 5.5 and in soil with a water content of wS=20% at pH 5.5. The results indicate that electroless amorphous Ni-P and Ni-Sn-p plating of the corrosion current density is 4.5% and 1.2% of the bare copper and the two coatings offer better corrosion resistance than copper in weak acidic corrosive medium, while Ni-Sn-P coating exhibits the best corrosion resistance. Besides, the two coatings have a negative shift of self-corrosion potential when compared with Cu substrate, showing a good application prospect as anodic protective coatings for Cu ground wires in acidic or weak acidic soil medium.