用电化学阻抗谱研究钢表面三种电镀镍层的耐蚀性

Corrosion preventive property of three kinds of electroplated nickel films on the steel surface using electrochemical impedance spectroscopy

在钢基体S 47220上分别电镀光亮、无光亮和多层镍镀层,采用电化学阻抗谱、极化曲线等研究在3.5%的Na Cl溶液中钢基体、纯镍和镀镍样品的腐蚀电化学行为,采用中性盐雾试验测试三种镀层的耐蚀性.结果表明,多层镍镀层比单一镍镀层表面更加致密,更难发生钢基体的优先腐蚀,因此保护性更好.钢基体、光亮镍镀层和无光镍镀层的等效电路模型分别是R_s(R_(ct)Q_(dl))(R_(pit)Q_(pit))、R_s(R_(ct)Q_(dl))(R_(pore)Q_(pore))和R_s(Q_(film)(R_(film)(R_(ct)Q_(dl)).在中性盐雾试验中,三层镍镀层经盐雾试验288 h后未发生腐蚀,因为其等效电路图Rs(RctQdl)与单质镍相同,具有相似的抗电化学腐蚀性能,所以耐蚀性优异,远高于单一镍镀层.

Bright nickel, dark nickel mono - layer and multi - layer nickel deposities were electrodeposited on S 47220 stainless steel samples. The electrochemical corrosion behaviors of steel substrate, pure nickel and nickel electroplated samples were studied in a 3.5wt % NaC1 solution by electrochemical impedance spectroscopy technology and polarization curves. Corrosion properties of the three kinds of nickel electroplated films were tested by neutral salt spray test （NSS）. Results showed that the multilayer nickel electroplated film has a better corrosion resistance and it is more dense and more difficult for the substrate to be corroded than mono -layer one. The equivalent circuits （EC） of subtrate, bright Ni and dark Ni mono - layer are RS （ Rct Qdl ） （ Rpitting Qpitting ）, Rs （ Rct Qdl ） （ Rpore Qvore ） and Rs （ Qfilm （Rfilm （ Rct Qdal ） , respectively. The three layer nickel electroptated film has not be corroded in NSS for 288h. It presents a same EC Rs （ Rct Qdl ） and a similar electrochemical corrosion performance to the pure nickel sample, so it has a much better anti - corrosion property than mono - layer one.