钙离子的浓度对X80钢腐蚀行为的影响

采用失重法、电化学测试、扫描电镜、X射线衍射等方法研究了钙离子浓度对X80钢在哈密土壤模拟溶液中的腐蚀行为影响.在60d浸泡期内,X80钢在不同钙离子浓度模拟溶液中的腐蚀形态均为全面腐蚀,腐蚀产物都为B-FeOOH;X80钢在模拟溶液中的腐蚀速率随钙离子浓度的降低而呈逐渐增大的趋势.在180d浸泡期内,在钙离子浓度为63.5mmol·L-1的模拟溶液中,钙盐随时间的增加在X80钢基体表面不断结晶析出;钙盐层有效阻碍了溶解氧的迁移,并促进其覆盖区域下形成氧浓差电池,最终导致基体表面点蚀的萌生.同时,在内层腐蚀产物表面连续析出的钙盐层的致密性也随时间不断得到改善,在一定程度上起到了抑制氯离子和溶解氧对基体的侵蚀作用,X80钢的全面腐蚀逐渐减缓. 

Effects of the concentration of calcium ions on the corrosion behavior of X80 steel

The effects of Ca2+ concentration on the corrosion behavior of X80 steel in Hami soil simulated solutions were investigated by using weight loss measurements, electrochemical testing, scanning electron microscopy (SEM), and X-ray diffraction (XRD). When the steel is immersed in the simulated solutions with different Ca2+ concentrations for 60 d, uniform corrosion occurs on the steel surface and the corrosion products mainly consist of β-FeOOH. The corrosion rate of the steel in the simulated solution gradually increases with the decrement of Ca2+ concentration. When the steel is immersed in the simulated solution with the Ca2+ concentration of 63.5 mmol·L-1 for 180 d, calcium salts continuously deposit on the steel surface to form a crystalline salt layer with the increasing of time. The calcium salt layer effectively hinders the migration process of dissolution oxygen, then promotes the formation of an oxygen concentration cell under its coverage region, and finally leads to the generation of pitting corrosion on the steel surface. At the same time, the compactness of the calcium salt layer that deposited on the inner corrosion product is gradually improved during this process, which can inhibit the corrosion effects of Cl- and dissolved oxygen on the steel to a certain extent, and also makes the uniform corrosion of the steel gradually slow down.