粗糙度在316L不锈钢小孔初期生长过程中的作用

Effect of Surface Roughness on Early Stage of Pitting Corrosion of 316L SS

通过分析不同粗糙度下的316L不锈钢在0.01 mol/L Na Cl溶液中小孔腐蚀早期的电流波动,研究了粗糙度与不锈钢亚稳态孔蚀电位Em和稳定孔蚀电位Eb之间的关系,以及粗糙度(Ra)对亚稳态小孔生长机制的影响。结果表明,Em和Eb均随Ra的对数的增大而线性下降;Ra增大,亚稳孔的平均形核率和平均寿命增大,生长速率变化不大,但是同样的生长速率下粗糙表面的亚稳孔具有更强的可持续生长能力,加之高的形核频率导致强的腐蚀累积效应促进了亚稳态小孔向稳定孔的转变。

The influence of the surface roughness(Ra) on the metastable pitting potential(Em) and the stable pitting potential(Eb) as well as on the growth mechanism of metastable pittings was studied by analyzing the current fluctuations at the early stages of pitting corrosion for 316 L stainless steel with three level of surface roughness. The results show that as lg Raincreases both Emand Eb values decrease linearly. With the increase in surface roughness, the average nucleation rate and lifetime of metastable pits decrease while its growth rate shows little change. But by the same growth rate the metastable pits on the steel with larger surface roughness has bigger sustained growth ability, which in combination with the accumulated corrosion damage resulted from high nucleation rate may be beneficial to the transformation of metastable pits into stable pits.