【作者】 陈振宇；

【导师】 郭兴蓬；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2010， 博士

【摘要】 缓蚀剂通过在金属与溶液之间的界面上起特殊的物理与化学作用来抑制腐蚀介质对材料的腐蚀。通过原子力显微镜分析手段,同时结合电化学方法来考察缓蚀剂对界面物理、化学性质的影响,从而更全面、更深入地阐明缓蚀剂的作用机理。在盐酸溶液中,十二烷基胺自发地吸附在碳钢表面,每个十二烷基胺分子平均取代1.1个吸附在金属上的水分子,通过其极性基团-NH2吸附在碳钢表面,而非极性基团-C12H13排列在酸液中,十二烷基胺分子垂直于碳钢表面组成单分子吸附层,并通过“几何覆盖效应”隔离了酸液与碳钢的接触,从而抑制了碳钢的腐蚀,同时十二烷基胺的吸附使得碳钢表面的润湿性减弱,并导致电极的零电荷电位向正方向移动。十二烷基胺在碳钢表面的吸附服从阿仑尼乌斯方程,十二烷基胺的吸附,导致腐蚀反应的活化能有所增加并且显著降低了指前因子,从而减缓了腐蚀反应速率。原子力显微镜电流图像表明碳钢表面有十二烷基胺吸附的部位导电性能显著下降,原子力显微镜力曲线则显示在无十二烷基胺吸附的碳钢表面无明显的黏附力,在有十二烷基胺吸附的表面存在均值为1.3nN的黏附力,从原子力显微镜电流图像可以观察到十二烷基胺在碳钢表面的吸附服从随机分布。在氯化钠溶液中,钼酸盐与铬酸盐均对碳钢腐蚀反应的阳极过程有明显抑制作用,在相同浓度下,铬酸盐不仅具有更好的均匀腐蚀抑制能力,而且具有更好的点蚀抑制能力。原子力显微镜I-V曲线测试表明铬酸盐与钼酸盐在碳钢表面形成了不导电的钝化膜,原子力显微镜形貌与力曲线测试结果表明铬酸盐在碳钢表面形成的钝化膜比钼酸盐形成的钝化膜更致密、更平整、硬度更高。通过小波变换可以将对应于点蚀过程的噪声提取出来,通过对提取出的噪声进行分析,发现添加缓蚀剂后亚稳态点蚀噪声的产生频率、幅值、寿命都显著下降,在相同浓度下,添加铬酸钠下降的程度比添加钼酸钠下降的程度更为明显。基于小波变换的尺度积分电量可以定量地评价缓蚀剂对亚稳态点蚀的抑制效率,结果表明铬酸钠对亚稳态点蚀的抑制效率强于钼酸钠。金属铜在氯化钠溶液中的阴极反应受氧扩散控制,当铜表面存在十二硫醇自组装膜时,阴极反应受到有效抑制,氧扩散不再是控制步骤。随着自组装时间的增加,缓蚀效率逐渐升高,循环伏安曲线氧化峰和还原峰的电流绝对值下降,试样表面的摩擦力逐渐减小。由于相对硫醇吸附膜的厚度,铜表面的粗糙度太高,从原子力显微镜形貌图上难以考察十二硫醇的吸附情况,而从原子力显微镜相位图可以观察到在十二硫醇溶液中自组装不同时间的铜电极表面存在着显著差异。相位图的多重分形谱f(α)-α显示空白铜试样所对应的多重分形谱△α与△f值较小,说明空白铜试样物性较均匀；铜试样在十二硫醇中自组装时间较短时,试样所对应的多重分形谱△α与△f值显著增加,表明试样表面不均匀性增加,即试样表面仅部分被十二硫醇自组装膜覆盖；当自组装时间较长时,所对应的多重分形谱△α与△f值再次下降,说明试样表面基本为十二硫醇自组装膜所覆盖。更多还原

【Abstract】 Since their special physical and chemical effects on the interface between metal and solution, inhibitors can prevent materials from corrosion. The effects of inhibitors can be investigated through atomic force microscopy (AFM) and electrochemical methods, and the inhibition mechanism can be further comprehensive studied.Dodecylamine can adsorb on carbon steel spontaneously in hydrochloric acid solution through its polar group(-NH2), and its non-polar group(-C12H13) is in hydrochloric solution and its direction is perpendicular to the metal surface. Each adsorption dodecylamine molecule replaces 1.1 water molecule on the metal surface, and dodecylamine molecules forms a monolayer film on carbon steel surface. The inhibition mechanism of dodecylamine for carbon steel is geometric blocking effect. Since dodecylamine forms a hydrophobic membrane on carbon steel surface, the wettability of the surface is reduced. The adsorption of dodecylamine on carbon steel surface is accord with Arrhenius equation, the adsorption increases apparent activated energy and reduces pre-exponential factor, thus decreases the corrosion rate. The adsorbed dodecylamine film also changed the structure of the double-electric layer and made the potential of zero charge shift to the positive direction. AFM force curves indicate that at the area without adsorbed dodecylamine, there is no obvious adhere force, however at the area with adsorbed dodecylamine, there is average 1.3nN adhere force.The anodic process of carbon steel in sodium chloride solution is inhibited significantly by molybdate and chromate, they can form nonconducting film on carbon steel surface. At the same concentration, the passive film formed by chromate is more compact and harder than that by molybdate. Chromate has better inhibition effect on carbon steel general and pitting corrosion. The noise corresponding to pitting corrosion can be picked up from the recorded signal based on wavelet transform. Through analysis of the picked up noise, it is learned that the pit nucleation rate, average current amplitude and lifetime of current transient, integrated current decreased with the addition of molybdate and chromate. The inhibition efficiency of chromate is higher than molybdate on carbon steel pitting corrosion. The cathodic process of copper in sodium chloride solution is controlled by oxygen diffusion, when there are self-assembled monolayers (SAMs) of dodecanethiol on copper surface, cathodic reaction is inhibited, oxygen diffusion is no longer control process. The absolute value of peak current in cyclic voltammetry curves and surface friction force decrease with the increase of self-assembling dodecanethiol time, the inhibition efficiency increases with the increase of self-assembling time, when the self-assembiling time reaches 40min, the surface is entirely covered by dodecanethiol, the inhibition efficiency changes little with the increase of self-assembiling time. Since the roughness of copper surface is very high, no important information can be got form AFM topography, but there’s big difference among the AFM phase images of copper surface by self-assembling dodecanethiol different time. The multifractal spectrum f(α)-αprovides important information for the adsorption of dodecanethiol, as for bare copper surface,ΔαandΔf value are small, which means the surface is very uniform, butΔαandΔf value increase greatly after self-assembiling dodecanethiol of a short time, which indicates the surface inhomogeneity increase, the surface is partly covered by dodecanethiol, a further self-assembly with dodecanethiol monolayer makesΔαandΔf decrease again, which indicates the surface is covered by dodecanethiol entirely and become uniform again.更多还原