电沉积方式对Ni-Cr-Mn合金镀层耐蚀性的影响

Effects of Electrodeposition Methods on Corrosion Resistance of Ni-Cr-Mn Alloy Coatings

采用直流、单脉冲和换向脉冲三种不同电沉积方式在Q235钢表面电镀制备Ni-Cr-Mn合金镀层。利用辉光放电光谱仪、形状测量激光显微系统、Tafel曲线和电化学阻抗谱,研究了电沉积方式对镀层元素含量、沉积速率、3D形貌和耐蚀性的影响。结果表明:按照直流、单脉冲和换向脉冲的顺序,镀层中镍含量减小,铬、锰含量增大,沉积速率先增大后减小,表面粗糙度降低,耐蚀性增强。直流方式制备的镀层表面存在个别较大的颗粒,单脉冲方式制备的镀层表面颗粒大小较为均匀,但仍存在个别较大颗粒,换向脉冲方式制备的镀层总体均匀致密。换向脉冲方式制备的镀层表面粗糙度最低,在3.5%NaCl溶液中,该镀层具有最大的腐蚀电位(-0.305 V)、最小的腐蚀电流密度(7.467×10^(-8)A·cm^(-2))和最大的电荷转移电阻(5972Ω·cm^2),耐蚀性最佳。

Ni-Cr-Mn alloy coatings were prepared on the surface of Q235 steel by electrodeposition methods such as direct current, single pulse current and pulse reverse current, respectively. The effects of electrodeposition methods on the element composition, deposition rate, 3D morphology and corrosion resistance of the coatings were investigated by glow discharge spectroscopy, laser microscope, Tafel curve and electrochemical impedance spectroscopy. The results show that in the order of direct current, single pulse current, and pulse reverse current, Ni content in the coatings decreases, Cr and Mn contents increase; the coating deposition rate increases firstly and then decreases; the surface roughness decreases; and the corrosion resistance strengthens. The occasionally individual big particles exists on the coating surface prepared by direct current electrodepositing and the coating prepared by single pulse current has relatively uniform particles on the surface, but there are occasionally individual big particles on the coating surface as well. The coating prepared by pulse reverse current is uniform and compact on the whole. The coating prepared by pulse reverse current has the lowest surface roughness. In 3.5% NaCl solution, the coating prepared by pulse reverse current has the maximum corrosion potential （-0.305 V）, the minimum corrosion current density （7.467× 10^-8 A·cm-2） and the maximum charge transfer resistance （5972 Ω· cm2）, which can exhibit the best corrosion resistance.