不同镀层对铜接地线在弱酸性介质中耐蚀性的影响

Influence of different coatings on corrosion resistance of copper ground wire under weak acid environment

以紫铜片为基体,采用电镀或化学镀法分别制备了Ni、Sn、Ni–P以及Ni–Sn–P镀层。通过测定Tafel极化曲线和电化学阻抗谱,对比研究了不同镀层在pH=5.5的3.5%NaCl溶液和pH=5.8、含水量20%的土壤中的电化学腐蚀性能。结果表明,4种镀层在所研究的酸性介质中均具有比金属铜更强的电化学极化阻力;化学镀Ni–Sn–P镀层在弱酸性介质中具有最好的耐蚀性;除电镀Ni层外,其他镀层的自腐蚀电位均负于铜基体,为阳极性镀层。根据所有实验结果的综合分析,可以预期,Ni–Sn–P和Ni–P镀层用作铜接地线在酸性或弱酸性土壤中的保护性镀层具有很好的应用前景。

Ni, Sn, Ni-P, and Ni-Sn-P coatings were prepared respectively on pure copper substrates by electroplating or electroless plating method. The electro- chemical corrosion properties of different coatings in 3.5% NaCl solution with a pH of 5.5 and in soil with a water content of 20% at pH 5.8 were comparably studied through the determination of Tafel polarization curves and electro- chemical impedance spectra. The results show that all of the coatings have stronger electrochemical polarization resistance than the pure copper in weak acid media. The electroless plated Ni-Sn-P coating has the best corrosion resistance in weak acid media. All the coatings except electroplated Ni coating have a negative shift of self-corrosion potential as compared with the copper substrate and can be used as anodic protection coatings. It is expected through analyzing all of the test results that Ni-Sn-P and NiP coatings have a good application prospect as the protective coatings for copper ground wires in acid or weak acid soil.