盐酸基溶液中铁离子对铁素体不锈钢腐蚀行为的影响

Corrosion Behavior of Ferritic Stainless Steel in Hydrochloric Based Acid with Ferrous and Ferric Ions

通过腐蚀失重测试、宏观形貌观察、微观形貌分析、自腐蚀电位测定、极化曲线以及交流阻抗图谱测试等试验检测方法,考察了盐酸溶液中铁离子对热轧抛丸后铁素体不锈钢表面氧化层去除过程的影响。结果表明:不锈钢酸洗过程中Fe2+的累积使溶液氧化还原电位降低,同时降低酸洗效率;Fe3+的累积使溶液氧化还原电位提升,同时提升酸洗效率。在3 mol/L盐酸浓度的溶液中,加入0.5 mol/L的Fe3+或Fe2+,不锈钢的酸洗失重率由0.22%分别增至1.23%或降至0.14%。随着溶液中Fe3+同Fe2+摩尔浓度比(CFe3+/CFe2+)的增大,不锈钢的酸洗失重率逐渐增大。在盐酸浓度为1.37 mol/L、全铁浓度为1.79 mol/L的溶液体系中,当CFe3+/CFe2+≥2时,不锈钢的酸洗失重率较不含铁离子的溶液体系提高7.2倍以上。在盐酸溶液中,Fe3+通过直接参与阴极反应提升反应速率,Fe2+通过替换不锈钢表面吸附的H+从而降低反应速率。

The effects of ferrous(Fe2+)and ferric(Fe3+)ions on pickling behaviour of originally hot-rolled and blasted ferrite stainless steel(FSS)in HCl-based electrolytes were investigated in this work through weight-loss test,macro profile,SEM morphology,self-corrosion potential test,polarization curves and electrochemical impedance spectroscopy measurements.The results demonstrated that the accumulation of Fe2+in the electrolytes for pickling FSS would lower both the self-corrosion potential and the weight-loss rate,meanwhile Fe3+had the opposite functions with higher self-corrosion potential and weight-loss rate.In the electrolytes of 3 mol·L-1HCl,0.5 mol/L Fe3+enhanced the weight-loss from 0.22%to 1.23%,while the same amount of Fe2+reduced it to 0.14%.By promoting the molar ratio of Fe3+and Fe2+(CFe3+/CFe2+)in the pickling electrolytes,the weight-loss rate of FSS would also increase accordingly.In the pickling electrolyte with 1.37 mol/L HCl and total ferrous and ferric ions of 1.79 mol/L,the weight-loss rate of FSS were enlarged 7.2 times or more than that without any ferrous and ferric ions when CFe3+/CFe2+≥2.It is concluded that in the pickling electrolyte with HCl,Fe3+acts directly in cathodic reactions to accelerate the pickling of FSS,and Fe2+replaces originally attached H+in the interface of FSS and the electrolyte to partially inhibit the pickling rate.