湿热工业海洋大气中Si对桥梁钢腐蚀行为的影响

Effect of Si on Corrosion Behavior of Model Bridge Steels by Alternative Wetting/drying Test in an Artificial Medium Simulated Hot and Humid Atmosphere of Marine and Industrial Area

以NaCl+NaHSO_3为腐蚀介质,通过周期浸润加速腐蚀实验、腐蚀失重、XRD、XPS、SEM/EDS和极化曲线等,研究了湿热工业-海洋大气环境中,Si对桥梁钢腐蚀行为的影响。结果表明:实验钢的腐蚀过程遵循幂函数分布规律。Si含量由0.25%(质量分数)增加到0.48%,实验钢的耐蚀性提高,但随锈层保护性增强,Si的作用有所减弱。Si在强化铁素体组织、细化腐蚀产物颗粒和促进铁氧化物结晶方面的作用显著,能使锈层的保护性在短时间内得到提升。同时Si在裂纹和锈巢边缘出现富集,一定程度上能帮助修复锈层缺陷。Fe_2SiO_4是Si在锈层中的主要存在形式,具有反尖晶石结构,能增强锈层的稳定性。

The effect of Si on the corrosion behavior of two model bridge steels by alternative wetting and drying test in an artificial medium of 0.1 mol/L NaCl＋0.01 mol/L NaHSO_3, which aims to simulate the atmosphere corrosion of marine and industrial area, was investigated by mass loss method, polarization curve measurement, X-ray diffraction and scanning electron microscope with energy spectrum. The results indicate that the corrosion process of the two steels follows fairly well a power function of W=Atn. When the Si content increases from 0.25%（mass fraction） to 0.48%,the weathering resistance of the two steels enhanced. However, with the increase of the thickness of the protective rust layer, the positive effect of Si weakened gradually. Si plays a significant role in strengthening ferrite microstructure, refining the grain size of corrosion products and promoting the crystallization of iron oxide, which enable the protectiveness of the rust layer to be increased in a short time. Besides, Si enriched in the edge of cracks and holes of the rust layer, that may be beneficial to the mending of defects. In the rust layer, Si exists mainly in the phase Fe_2SiO_4, which has an inverse spinel structure, and thus can enhance the stability of the rust layer.