Pramod Kumar Uppalapati, Liang Tongxiang, Kennady C Joseph, Nandha Kumar Raju, Prabhu Jayaraj
School of Materials Science and Engineering, Jiangxi University of Science and Technology, 156, Hakka Road, Ganzhou 341000, P. R. China.
Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur Campus, Chennai 603203, Tamil Nadu, India.
ACS Omega. 2020 Feb 12;5(7):3376-3388. doi: 10.1021/acsomega.9b03599. eCollection 2020 Feb 25.
Herein, Ni-W alloy matrixes were successfully fortified with two salen-type Schiff bases 1-(()-(2-(()-(2-hydroxynaphthalen-1-yl)methyleneamino)phenylimino)methyl)naphthalen-2-ol (OPD) and 1-(()-(2-(()-(2-hydroxynaphthalen-1-yl)methyleneamino)phenylimino)methyl)naphthalen-2-ol (PPD) as additives, of similar molecular structure but varied isomeric spacers, using a facile direct current electrodeposition technique. The resulting coatings from the additive-introduced reaction system were termed as Ni-W/OPD and Ni-W/PPD throughout the study. The deterioration process (0.5 M HSO), surface properties, elemental composition, functional groups, and structurs of the resultant coatings were analyzed by means of Tafel and electrochemical impedance spectroscopy, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction (XRD). The bare Ni-W alloy deposition resulted in a loose microstructure with higher porosity density (12.2%), while that of additive-doped plating electrolytes resulted in a compact and dense microstructure with lesser porosity density (6.3%) and minimal porosity density (3.7%) as for Ni-W/OPD and Ni-W/PPD alloy coatings, respectively. Improved corrosion parameters presented superior corrosion characteristics of Ni-W alloy coatings from an additive (PPD)-induced bath, i.e., Ni-W/PPD. Synergetic adsorption of imine groups (N atoms), hydroxyl groups (O atoms), and aromatic electron clouds and reduction in steric hindrance produced by a larger isomeric spacer strengthened the surface adsorption of additives, yielding a fine nanocrystalline Ni-W coating with reduced porosity and well-refined grains, implying the outstanding shielding effect. Results of FESEM, AFM, and XRD analyses revealed a complete cohesion between two neighboring islands, resulting in a fine planar structure with minimal coating defects for Ni-W/PPD coatings, authenticating the corrosion parameters.
在此，采用简便的直流电沉积技术，成功地用两种具有相似分子结构但异构间隔基不同的双水杨醛缩乙二胺型席夫碱1-（（（2-（（（2-羟基萘-1-基）亚甲基氨基）苯基亚氨基）甲基）萘-2-醇（OPD）和1-（（（2-（（（2-羟基萘-1-基）亚甲基氨基）苯基亚氨基）甲基）萘-2-醇（PPD）对镍钨合金基体进行了强化。在整个研究过程中，将添加剂引入反应体系所得到的涂层称为Ni-W/OPD和Ni-W/PPD。通过塔菲尔曲线和电化学阻抗谱、场发射扫描电子显微镜（FESEM）、X射线光电子能谱、原子力显微镜、能量色散X射线光谱、傅里叶变换红外光谱和X射线衍射（XRD）对所得涂层在劣化过程（0.5 M HSO）中的表面性能、元素组成、官能团和结构进行了分析。裸镍钨合金沉积物呈现出疏松的微观结构，孔隙率密度较高（12.2%），而添加剂掺杂的镀液所形成的沉积物则形成致密的微观结构，孔隙率密度较小，对于Ni-W/OPD和Ni-W/PPD合金涂层，孔隙率密度分别为6.3%和3.7%。改进后的腐蚀参数表明，添加剂（PPD）诱导镀液所形成的镍钨合金涂层，即Ni-W/PPD，具有优异的腐蚀特性。亚胺基（N原子）、羟基（O原子）和芳香电子云的协同吸附以及较大的异构间隔基所产生的空间位阻的减小，增强了添加剂的表面吸附，形成了孔隙率降低且晶粒细化良好的精细纳米晶镍钨涂层，这意味着具有优异的屏蔽效果。FESEM、AFM和XRD分析结果表明，相邻两个岛之间完全粘结，形成了Ni-W/PPD涂层的具有最小涂层缺陷的精细平面结构，证实了腐蚀参数。
