织构对纳米晶纯镍镀层耐蚀性能的影响

采用脉冲电镀法在黄铜表面制备出具有(111)、(200)和(220)晶面择优生长织构的纳米晶纯镍镀层.采用扫描电镜对镀层的显微形貌进行观察,采用X射线衍射对不同晶面织构的择优性进行表征,并对镀层在3.5%NaCl溶液中的动电位极化曲线和交流阻抗谱进行了测试,研究不同织构镀层的耐蚀性能.不同织构镀层的耐蚀性能存在显著差异:具有(220)强织构的镀层耐蚀性最差,其自腐蚀电流密度最大,为1.23μA·cm-2,镀层的电荷转移电阻为2.09kΩ·cm2;具有(200)强织构的镀层耐蚀性能最佳,镀层的电荷转移电阻为27.32kΩ·cm2,自腐蚀电流密度为0.15μA·cm-2;具有(111)织构镀层的耐蚀性居中.认为织构引起的表面胞状物的差别是造成纯镍镀层耐蚀性能不同的原因. 

Effect of textures on the corrosion resistance of nanocrystalline Ni coatings

Nanocrystalline Ni coatings with (111), (200) and (220) textures were respectively pulse-electrodeposited on brass. Scanning electron microscopy (SEM) was used to observe their microstructures, X-ray diffraction (XRD) analy-sis was adopted to identify the texture degree, and the anodic polarization curves and electrochemical impedance spectra were tested to investigate the corrosion resistance of the pulse-electrodeposited Ni coatings in 3.5% NaCl solution. An obvious difference in corrosion resistance exists among the coatings with different textures. The coating with (220) texture exhibits the worst corrosion resistance, with the corrosion current density of about 1.23μA·cm-2 and the coating polarization resistance of 2.09 kΩ·cm2; the coating with (200) texture has the best corrosion resistance, with the corro-sion current density of about 0.15μA·cm-2 and the coating polarization resistance of about 27.32 kΩ·cm2; the coating with (111) texture shows a corrosion resistance in between. The difference of surface island microstructures incurred by growth textures might be the reason for the different corrosion resistances of the as-deposited Ni coatings.