重铬酸根与磁场对铁在硫酸溶液中阳极极化行为的影响

EFFECT OF MAGNETIC FIELD AND DICHROMATE ON ANODIC POLARIZATION BEHAVIOR OF IRON IN SULFURIC ACID

采用动电位极化曲线法研究了外加磁场及不同浓度重铬酸根对Fe在 0 .5mol/LH2 SO4 溶液中阳极极化行为的影响 .结果表明 :浓度≤ 0 .0 2mol/L的重铬酸根不改变阳极极化曲线的构型 ;重铬酸根浓度≥ 0 .0 5mol/L时 ,阳极极化曲线上出现传质控制特征的斜率突变转折段 ,并且随重铬酸根浓度增大 ,斜率转折段在更负的电位、更小的电流密度下出现 .外加磁场后 ,不同阳极电位区间内会表现出电流变小、不变及增大的现象 ,这与相应电位下阴、阳极反应贡献的相对大小以及各自的控制步骤类型有关 .考虑阳极过程中可能发生的活性溶解、表面膜生成及表面膜溶解反应 ,以及阴极反应的影响 ,主要考虑磁场对阴、阳极反应中传质过程的作用 ,得出了外加磁场作用下的极化曲线模型 ,该模型较好地说明了磁场对不同电位区间电流密度产生不同影响的实验事实 .

The effects of magnetic field and dichromate ion with different concentrations on anodic polarization behavior of iron in 0.5 mol/L sulfuric acid were studied by means of potentiodynamic polarization measurements.Results showed that less than or equal to 0.02 mol/L dichromate did not change the configuration of the anodic polarization curve; anodic polarization curves showed drastic change of the slope for E-i curve when dichromate concentration was more than or equal to 0.05 mol/L, and such drastic slope changing occurred at more negative potential and low current density when dichromate concentration increased.Current densities would decrease, remain unchanged ,and increase in the presence of magnetic field in certain potential ranges, and such magnetic field effect was closely related to the contribution of the cathodic and anodic reactions and the type of rate controlling steps for each reaction. Magnetic field could accelerate the mass transfer process at electrode/solution interface, thus obviously increase the current density at the slope drastic changing section of the anodic polarization, even eliminate such a section.Magnetic field could induce new current oscillation, change the pattern of the pre-existing current oscillation, or even eliminate current oscillation.Activation-passivation transition occurred at more noble potential and higher current density in the presence of magnetic field than that in the absence of magnetic field.The model of polarization curve with magnetic field was derived based on taking into account of the possible active dissolution,film formation and film dissolution reactions in anodic process, the effect of cathodic reactions, and the effect of magnetic field on mass transfer processes in cathodic and anodic reactions.The model developed here matched well with the experimental results that magnetic field resulted in different effects on current densities in different potential ranges.