咪唑啉与碘化钾对钢在醋酸中的缓蚀协同效应

Synergistic inhibition effect of imidazoline and potassium iodide on cold rolled steel in acetic acid

采用失重法、动电位极化曲线法、电化学阻抗图谱(EIS)及扫描电子显微镜(SEM)研究了咪唑啉(IM)与碘化钾(KI)对冷轧钢在1.0 mol·L^(-1)醋酸(CH_(3)COOH)介质中的缓蚀协同效应。结果表明,单独咪唑啉对冷轧钢有良好缓蚀效果,缓蚀率随温度和咪唑啉浓度的升高而增大,50℃时最高可达到82%;加入KI复配后,缓蚀效果提高,50℃时达到了90.1%;且缓蚀协同效应系数大于1,两者存在缓蚀协同效应。IM与KI复配前后在钢表面的吸附规律均符合Langmuir吸附等温式,IM/KI复配后吸附平衡常数(K)进一步增大,而标准吸附Gibbs自由能(ΔG^(e))进一步变负。IM、KI、IM/KI均为以阴极抑制为主的混合型缓蚀剂,且IM/KI复配后腐蚀电流密度较复配前明显减小;Nyquist图谱主要包含高频区的容抗弧和低频区的感抗弧,IM与KI复配后电荷转移电阻增加。SEM微观形貌分析得出,IM与KI复配后更为有效地降低了醋酸对钢表面的侵蚀。

The synergistic corrosion inhibition effect of imidazoline(IM)and potassium iodide(KI)on corrosion of cold rolled steel in 1.O mol·L^(-1)acetic acid(CH_(3)COOH)medium was studied using weight loss method,potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS)and scanning electron microscopy(SEM).The results show that individual imidazoline acts as an efficient inhibitor for the corrosion of CRS,and the inhibition efficiency increases with the increase of temperature and concentration,reaching a maximum of 82%at 50℃.Incorporation of IM with KI results in a further improving inhibition,and the maximum inhibition efficiency can reach as high as 90.1%at 50 C.The synergistic coefficients are all greater than 1,indicating that there is a true synergistic effect of IM with KI.The adsorption of IM,IM/KI on CRS surface conform to Langmuir adsorption isotherm.The adsorption equilibrium constant(K)and the absolute adsorption Gibbs free energy(ΔG^(e))after IM/KI combination further turn to become more higher.IM,KI,BTA/KI are all mixed-type inhibitors while mainly retard the cathodic reaction and the corrosion current density after IM/KI combination is significantly dropped compared to before combination,confirming the synergism between IM and KI.Nyquist spectrum mainly contains the capacitive arc in the high-frequency region and the inductive arc in the low-frequency region.After the combination of IM and KI,the charge transfer resistance further increases to more extent.SEM clearly indicates that the combination of IM and KI can significantly reduce the corrosion degree of steel surface attacked by acetic acid.