稀土添加剂对Ni-Fe合金镀层制备及耐蚀性能的影响

采用稀土盐CeCl₃为添加剂,通过调整镀液中CeCl₃浓度在20#钢基体上电沉积制备Ni-Fe合金镀层.采用SEM,EDS和XRD等表征镀层的结构,采用电化学极化曲线和阻抗谱研究合金镀层在3.5%(质量分数)NaCl溶液中的耐蚀行为.结果表明:稀土添加剂在低pH值酸性体系中极易生成Ce(OH)₃溶胶,抑制 (FeOH) 和Fe(OH)₂等化合物的生成,其阴极吸附特性与 (FeOH) 的吸附形成竞争,优先吸附于材料表面,从而抑制了Fe的析出;另一方面CeCl₃的加入大大提高了电流效率,使镀速增大.当CeCl₃的浓度为3 g/L时,镀层中Fe的含量控制在16%左右,获得较好的镀层质量及较好的耐蚀性能.

Influence of Rare Earth Additive on Preparation and Corrosion Resistance of Ni-Fe Alloy Coating

The Ni-Fe alloy coating with Ce was electroplated on the 20# steel by adjusting the concentration of CeCl₃ in plating solution with the rare earth cerium salt CeCl₃ as the additive. The relevant microstructure and corrosion behavior in 3.5%NaCl solution of coatings were studied by means of SEM, EDS and XRD, as well as electrochemical polarization curve and impedance spectroscopy. The results indicate that rare earth additive in acidic bath is extremely favor of the generation of sol Ce(OH)₃, but restrains the generation of (FeOH) and Fe(OH)₂ etc. With cathodic adsorptive characteristics the adsorption of Ce(OH)₃ would compete with the adsorption of (FeOH). The former is preferentially absorpt on the surface of material, which restrains the generation of Fe. On the other hand, the addition of CeCl₃ improves the current efficiency greatly, so as to increase the deposition rate. When concentration of CeCl₃ is 3 g/L, the coating with better quality and better corrosion resistance would be obtained with the content of Fe controlled to about 16%.