钢铁点蚀坑内腐蚀产物对点蚀扩展的影响

Influence of Solid Corrosion Products in Corrosion Pits on Growth of Corrosion Pits

为了探讨钢铁点蚀坑内部生成的腐蚀产物对点蚀生长的影响,使用自制的2种铁微电极,通过电化学三电极体系,使之在阳极极化条件下发生溶解,一定程度上模拟点蚀生长的特征。结果表明:采用微型注射器可以将2种铁微电极表面黑色腐蚀产物沉积层冲洗到模拟点蚀坑外部,消除其对点蚀扩展的影响;通过对比冲洗前后的阳极溶解电流随时间的变化趋势,可以计算该腐蚀产物对模拟点蚀生长速率的影响;借助2种铁微电极的特殊性,提出了对其点蚀内部腐蚀产物影响进行量化的方法,将其用于修正点蚀内部金属离子的扩散系数,在一定程度上可完善点蚀的生长和预测模型。

In order to study the effect of solid corrosion products within corrosion pits on the growth of corrosion pits, the homemade iron micro- electrodes were dissolved under anodic polarization conditions by 3-electrode electrochemical system, which was used to simulate the features of corrosion pits. Results showed that on the surface of iron microelectrode, a deposition layer of black corrosion products was observed, which could be removed out by the flushing of a micro-syringe to eliminate its influence of the layer. By comparing the relationship between anodic current and time before and after flushing, the effect of corrosion products on the growth rate of the simulated corrosion pits could be calculate. Moreover, according to the characteristics of microelectrode, the method for quantification of the effect of corrosion products inside corrosion pits was put forward, which could correct the diffusion coefficient to improve and perfect the models of corrosion pit growth and prediction to a certain extent.