SO_2质量分数对污染海洋大气环境中高强钢E690腐蚀行为的影响

采用干湿交替腐蚀试验方法,结合电化学测试、锈层截面和腐蚀产物X射线衍射(X-ray diffraction,XRD)分析,研究SO_2质量分数对E690钢在模拟污染海洋大气环境中腐蚀行为的影响。结果表明,海洋大气环境中的SO_2改变了E690钢海洋大气腐蚀的电化学机制,使得极化曲线的阳极分支由弱钝化特征转变为活性溶解特征,阴极分支由氧扩散过程控制转变为氧扩散和析氢反应共同控制,因而大大促进了阳极和阴极的电化学反应过程。同时,SO_2又显著促进α-Fe OOH的生成和Ni、Cr合金元素在内锈层中的富集,大大促进锈层的致密化,使均匀腐蚀速率逐渐减低,并促进锈层底部点蚀坑的生长。随着模拟溶液中Na HSO_3浓度的增加,E690钢在60 d内的平均腐蚀速率逐渐增加,当Na HSO_3浓度达到0.03 mol/L时,又出现一定程度的降低;同时,锈层底部的点蚀坑随Na HSO_3浓度的增加显著长大。

Effect of SO2 Content on Corrosion Behavior of High-strength Steel E690 in Polluted Marine Atmosphere

Dry/wet cyclic corrosion tests, combined with electrochemical measurements, cross-sectional morphology observation of rust layer and X-ray diffraction (XRD) analysis of corrosion products, are conducted to investigate the effect of SO2 content on corrosion behaviors of E690 steel in simulated polluted marine atmosphere. The results show that SO2 can change the electrochemical corrosion mechanism of E690 steel in marine atmosphere. The anodic branch is transformed from weak passivation to active dissolution feature while the cathodic branch is transformed from oxygen diffusion process to mixed-control of oxygen reduction reaction and hydrogen evolution reaction, leading to great acceleration of anodic and cathodic reaction process. Meanwhile, SO2 can significantly promote the formation ofα-FeOOH and enrichment of Nickel and Chromium in the inner rust layer, resulting in the decrease of uniform corrosion rate and growth of corrosion pits under the rust layer. With the increase of NaHSO3 concentration, the average corrosion rate of E690 steel within 60 days in simulated marine atmosphere is increased accordingly, and then appears a certain degree of decline when the concentration of NaHSO3 obtained 0.03 mol/L. Meanwhile, the corrosion pits under the rust layer grew up significantly with the increase of NaHSO3 concentration.