弹性拉应力下Q235碳钢在5%NaCl盐雾中的成锈行为及其机理  

Rust Formation Behavior and Mechanism of Q235 Carbon Steel in 5%NaCl Salt Spray Under Elastic Tensile Stress

作　　者：李谦[1] 刘凯 赵天亮 LI Qian;LIU Kai;ZHAO Tianliang(State Key Laboratory of Advanced Special Steel,School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学材料科学与工程学院、省部共建高品质特殊钢冶金与制备国家重点实验室,上海200444

出　　处：《金属学报》2023年第6期829-840,共12页Acta Metallurgica Sinica

基　　金：国家重点研发计划项目No.2017YFB0702100;上海市青年科技英才扬帆计划项目No.20YF1412900

摘　　要：结合中性盐雾实验和四点弯曲法研究Q235碳钢在弹性拉应力作用下的预腐蚀成锈行为,采用SEM、XRD和电化学阻抗谱等手段研究了锈层的成分、结构以及电化学特性。结果表明,弹性拉应力通过加速阳极溶解促进锈层中γ-FeOOH物相的生成,且由于γ-FeOOH是在液相中生成,而γ-FeOOH向α-FeOOH和Fe_(3)O_(4)/γ-Fe_(2)O_(3)转化是在固-液界面进行,γ-FeOOH的生成速率比其转化速率快,导致锈层中γ-FeOOH的质量分数随应力水平提高而增加,α-FeOOH和Fe_(3)O_(4)/γ-Fe_(2)O_(3)的质量分数相应减少。随着应力由0增大至0.95σs(σs为屈服强度),Fe_(3)O_(4)/γ-Fe_(2)O_(3)的质量分数由53%减小至约46%,α-FeOOH的质量分数由约30%减小至约23%,γ-FeOOH的质量分数由不到17%增大至约31%,这种物相成分变化导致锈层的致密性降低,厚度增加。此外,弹性拉应力通过加速阳极溶解促进了锈层的生长,进一步增加了锈层的厚度。锈层的厚度增加提高了离子在锈层中电迁移的阻力,锈层的致密性降低减弱了锈层内侧微环境的闭塞性,2者的共同作用使得锈层的保护性随应力水平的提高呈增强趋势。As a structural steel material,carbon steel bears a certain extent of elastic tensile stress in actual service.Elastic tensile stress on steel is supposed to impact the electrochemical process and corrosion behavior,which may further influence the rusting behavior and the phase composition and structure of the formed rust layer.However,stresses on the steel substrate slightly influence the rust layer of carbon steel because no intrinsic change exists in the corrosion mechanism.Here,a remarkable effect of elastic tensile stress on Q235 carbon steel was found on the phase composition and structure of the rust layer formed in 5%NaCl salt spray.The effect on the rust layer was studied using SEM,XRD,and electrochemical impedance spectroscopy.The neutral salt spray test with four-point bending was used to preform the rust layer of Q235 steel under various stress levels.The results show that the elastic tensile stress accelerates the anodic dissolution,thereby promoting the generation ofγ-FeOOH,which occurs faster in the electrolyte than the transformation ofγ-FeOOH toα-FeOOH and Fe_(3)O_(4)/γ-Fe_(2)O_(3) in the solid-liquid interface.Consequently,the mass fraction ofγ-FeOOH in the rust layer increases as the stress level increases,whereas the mass fraction ofα-FeOOH and Fe_(3)O_(4)/γ-Fe_(2)O_(3) decreases accordingly.As the stress increases from 0 to 0.95σs(σs is yield strength),the mass fraction of Fe_(3)O_(4)/γ-Fe_(2)O_(3) decreases from 53%to~46%,the mass fraction ofα-FeOOH decreases from~30%to~23%,and the mass fraction ofγ-FeOOH increases from less than 17%to~31%.Meanwhile,the phase composition change decreases the density and increases the thickness of the rust layer.Additionally,the acceleration of the anodic dissolution induced by the elastic tensile stress promotes the growth of the rust layer,which further increases the thickness of the rust layer.The increase in thickness and decrease in compactness of the rust layer jointly enhance the protective capability of the rust layer.The former increases

关 键 词：弹性拉应力 碳钢 物相成分 结构 保护机制 

分 类 号：TG172.3[金属学及工艺—金属表面处理]