电沉积方式对镍-锡-锰合金镀层耐蚀性的影响

Effect of electrodeposition methods on corrosion resistance of Ni-Sn-Mn alloy coating

采用直流(DC)、脉冲(PC)和超声脉冲(UPC)电沉积方式在Q235钢表面制备Ni-Sn-Mn合金镀层,利用扫描电子显微镜(SEM)、辉光放电光谱仪(GDS)、X射线衍射仪(XRD)、Tafel曲线和电化学阻抗谱(EIS)研究了不同电沉积方式对镀层表面形貌、元素含量、沉积速率、相结构和耐蚀性的影响。结果表明,分别采用直流、脉冲、超声脉冲电沉积方式制备的镀层,Ni和Sn质量分数依次减小,Mn质量分数依次增大,沉积速率依次提高;直流电沉积镀层晶粒粗大,存在裂纹和孔隙,耐蚀性较差;脉冲电沉积镀层晶粒细化,无明显缺陷,耐蚀性较高;超声脉冲电沉积镀层均匀致密,呈非晶结构,在3.5%Na Cl溶液中具有最正的自腐蚀电位(-0.346 V)、最低的自腐蚀电流密度(3.162×10^(-8)A/cm^2)和最大的电荷转移电阻(9 143Ω·cm^2),镀层耐蚀性最好。

Ni-Sn-Mn alloy coatings are prepared on the surface of Q235 steel by direct current（ DC）,pulse current（ PC） and ultrasonic-pulse current（ UPC） electrodeposition methods respectively. The effects of electrodeposition methods on surface morphology,element content,deposition rate,phase structure and corrosion resistance are investigated by means of scanning electron microscopy（ SEM）,glow discharge spectroscopy（ GDS）,X ray diffractometer（ XRD）,Tafel polarization curve and electrochemical impedance spectroscopy（ EIS）. The results show that the mass fractions of Ni and Sn in coatings prepared by DC,PC and UPC electrodeposition methods respectively decrease in turn,but that of Mn increases in turn. Deposition rate of coatings prepared by DC,PC and UPC electrodeposition methods respectively increases in turn. The coating electrodeposited by DC has coarse grains,cracks and voids,and exhibits poor corrosion resistance. The coating electrodeposited by PC has fine grains and no obvious defect,and shows higher corrosion resistance.The coating prepared by UPC electrodeposition is most uniform and dense,possesses amorphous structure,and exhibits the most positive self-corrosion potential（-0. 346 V）,the smallest corrosion current density（ 3. 162 × 10^（-8） A·cm-2） and the biggest charge transfer resistance（ 9 143 Ω·cm^2） in 3. 5% Na Cl solution,representing the best corrosion resistance among three coating samples.