NH_4Cl薄层液膜下X70钢腐蚀的电化学研究

采用电化学阻抗法和阴极极化曲线法研究了X70钢在含NH4Cl薄层液膜下的电化学行为.研究了液膜厚度、NH4Cl浓度对X70钢腐蚀行为的影响.结果表明,液膜厚度降低,X70钢腐蚀电位正移,阴极极限扩散电流增大.液膜厚度为130μm时,阴极极限扩散电流达最大值.液膜厚度为130~100μm时,阴极极限扩散电流反而降低.液膜厚度进一步减薄,阴极极限扩散电流又增大.薄层液膜下,NH4Cl浓度增大,阴极极限扩散电流减小,抑制了阴极过程;随着NH4Cl浓度增大,X70钢腐蚀的电荷传递电阻减小,对阳极过程有一定的促进作用,从而加速X70钢的腐蚀速率.

Electrochemical Study on Corrosion of X70 Steel under Thin Layer of Electrolytes Containing NH4Cl

The corrosion of X70 steel under thin electrolyte layer containing NH4Cl was studied by cathodic polarization and electrochemical impedance spectroscopy. The influence of layer thicknes and NH4Cl concentration were examined. The results showed that the corrosion potential and the cathodic diffusion limiting currents increased with the decreasing of the layer thickness. The critical thickness for maximum cathodic diffusion limiting current was about 130 μm. In the range of 130 μm to about 100 μm, the cathodic diffusion limiting current was slightly decreased. The further decreased in the electrolyte layer thickness increased the cathodic diffusion limiting current to some extent again. Under thin electrolyre layers, with the increasing of NH4Cl concentration, the cathodic diffusion limiting currents decreased, the cathodic process was nhihited. With increasing NH4Cl concentration, the charge transfer resistance of X70 steel decreased and the anodic process was promoted, the corrosion rate of X70 steel was accelerated.