【作者】 姜晶；

【导师】 王佳；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2009， 博士

【摘要】 金属表面的液相状态是影响气/液/固多相体系腐蚀行为的重要因素,其中液相分散程度是评价气/液/固多相分散腐蚀体系的主要液相状态特征,与气/液/固三相线界面区的物理特性密切相关。气/液/固三相线界面区定义为气/液/固三相交界线向液相区域内0～100μm液膜厚度范围内的液相反应区域。三相线界面区是比溶液本体相更强的高速阴极反应区,其阴极反应速度取决于三相线界面区面积以及三相线界面区分布状态。液相分散程度可以由液相边缘三相线界面区的长度及宽度参数来进行描述,因此研究三相线界面区的性质对气/液/固多相体系腐蚀行为的影响能反映出液相分散程度在气/液/固多相体系腐蚀过程中的作用。本论文采用稳态极化技术、电化学阻抗谱、线性极化电阻技术、接触角测量技术以及显微镜观察技术,分别研究了三相线界面区的长度、宽度及液膜浓度对氧还原阴极过程及腐蚀行为的影响。研究结果表明,三相线界面区长度及宽度对金属腐蚀阴极过程及腐蚀行为有重要影响。测得的阴极极限电流密度及腐蚀电流密度均随单位面积的三相线长度及宽度的增加而线性增加,且单位三相线长度从0增加到1 cm-1时,阴极极限电流密度近似增加一倍,相当于电极反应面积增加了一倍,表明三相线界面区对阴极行为具有很大的影响,是不能忽视的。从腐蚀的角度来说,分散的液相比集中液相更能够加速材料的大气腐蚀过程。气/液/固多相分散腐蚀体系是广泛存在,因而这是一个必须重视的重要现象。为了进一步探寻三相线界面区加速阴极过程的作用机理,采用Kelvin探针技术研究了三相线界面区的阴极极限电流密度随液膜厚度的变化规律,初步建立了三相线界面区阴极过程模型,并在此基础之上建立了三相线界面区加速阴极氧还原过程的作用机理模型。大气及土壤腐蚀体系均为典型的气/液/固多相分散腐蚀体系,液相在金属表面以高度分散态存在,因此液相分散程度对金属腐蚀行为有重要影响。对于大气腐蚀,结合分形定律,建立了液相分散程度与三相线界面区参数的相关性,并在此基础之上,模拟研究了液相分散程度对大气腐蚀行为的影响。模拟结果表明,大气腐蚀阴极极限扩散电流随液相分散程度的增加而线性增加,证实了液相分散程度对大气腐蚀行为的重要影响。在砂土腐蚀体系中,首先研究了液相分散程度及三相线界面区参数随砂土含水量的变化,在此基础之上建立了液相分散程度影响砂土体系腐蚀行为的作用机理模型。模型计算结果表明,砂土体系的阴极极限电流同样随液相分散程度的增加而线性增加,证实了液相分散程度对砂土体系腐蚀行为的重要影响。更多还原

【Abstract】 Liquid state on a metal surface is an important factor influencing corrosion behavior of metals in gas/liquid/solid multiphase corrosion systems. Liquid dispersion, one of important properties of liquid state, is closely related with the geometric properties of gas/liquid/solid three-phase boundary (TPB) zone of dispersive liquid on the metal surface. Therefore, studies of effects of geometric properties of TPB zone on cathodic and corrosion behavior of metals can reflect the important role of liquid dispersion in gas/liquid/solid multiphase corrosion systems.In this paper, steady-state polarization technique, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) technique, contact angle measurement technique, combined with microscopic observation technique, are employed to investigate the influence of TPB length, width and electrolyte concentration on cathodic and corrosion behavior of metals. The results show that both the cathodic limiting current density and corrosion current density linearly increase with increasing the TPB length and width, indicating that the liquid dispersion plays an important role in gas/liquid/solid multiphase corrosion systems.Further, a Kelvin probe technique is used to study the effect of electrolyte layer thickness on the cathodic limiting current density of TPB zone. On this basis, a model is developed to simulate the cathodic oxygen reduction process in this zone. Based on this model, effects of TPB geometric parameters on the cathodic limiting current density of metals are simulated, and the calculated results are in good agreement with the experimental data.Atmospheric and soil corrosion systems are typical of gas/liquid/solid multiphase and dispersive corrosion systems, in which liquid dispersion plays a vital role in the corrosion processes of metals. In atmospheric corrosion, the correlation between the liquid dispersion and TPB parameters is established, and the influence of liquid dispersion on the cathodic oxygen reduction process of atmospheric corrosion is simulated. The simulation results show that the cathodic limiting current of metals is linearly dependent on the liquid dispersion, confirming the important role of liquid state in atmospheric corrosion systems. In sandy soil corrosion, the variations of both TPB parameters and liquid dispersion with soil water content are investigated, and on this basis, the influence of liquid dispersion on the cathodic oxygen reduction process of sandy soil corrosion is simulated. The simulation results show that the cathodic limiting current density of metals linearly depends on the liquid dispersion, further confirming the important role of liquid state in sandy soil corrosion systems.更多还原