Onyeachu Ikenna B, Abdel-Azeim Safwat, Chauhan Dheeraj Singh, Quraishi Mumtaz A
Africa Centre of Excellence in Future Energies and Electrochemical Systems (ACE-FUELS), Federal University of Technology, Owerri PMB 1526, Nigeria.
Center of Research Excellence in Corrosion, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
ACS Omega. 2020 Dec 23;6(1):65-76. doi: 10.1021/acsomega.0c03364. eCollection 2021 Jan 12.
An expired metformin drug (MET) was used as a corrosion inhibitor for C1018 carbon steel in a CO-saturated 3.5 wt % NaCl + 340 ppm acetic acid solution under static conditions. The inhibitor was evaluated using electrochemical methods complemented with surface analytical measurements and computational modeling. The drug displayed a high inhibition efficiency of ∼90% at 200 ppm. Impedance analyses revealed a rise in the charge transfer resistance at the steel-solution interface upon the addition of the inhibitor. Polarization measurements suggested that MET acted more like a cathodic-type corrosion inhibitor and significantly reduced the corrosion current density. The adsorption of MET on the steel substrate followed the Langmuir isotherm, showing a mixed type of physical and chemical modes of adsorption. The thermodynamic parameters revealed strong and spontaneous adsorption on the steel surface. The surface analysis using SEM supported the inhibitor adsorption on the steel substrate. Based on the DFT simulation, inhibition by MET is mainly achieved by its protonated form, which leads to the formation of a thin film on the steel surface rather than the modification of the work function of the steel surface. The experimental and theoretical estimations of pa complemented the DFT results, both agreeing that the monoprotonated form of MET is the dominant form in which the inhibitor adsorbs on the steel surface to form a thin film rather than modify the work function of the steel surface.
在静态条件下，将过期的二甲双胍药物（MET）用作C1018碳钢在CO饱和的3.5 wt％NaCl + 340 ppm乙酸溶液中的缓蚀剂。使用电化学方法并辅以表面分析测量和计算模型对该缓蚀剂进行了评估。该药物在200 ppm时显示出约90％的高缓蚀效率。阻抗分析表明，添加缓蚀剂后钢-溶液界面处的电荷转移电阻增加。极化测量表明，MET的作用更像是阴极型缓蚀剂，并显著降低了腐蚀电流密度。MET在钢基体上的吸附遵循朗缪尔等温线，呈现出物理和化学混合的吸附模式。热力学参数表明在钢表面有强烈且自发的吸附。使用扫描电子显微镜（SEM）进行的表面分析支持了缓蚀剂在钢基体上的吸附。基于密度泛函理论（DFT）模拟，MET的缓蚀作用主要通过其质子化形式实现，这导致在钢表面形成一层薄膜，而不是改变钢表面的功函数。对pa的实验和理论估计补充了DFT结果，两者均一致认为MET的单质子化形式是缓蚀剂吸附在钢表面形成薄膜而非改变钢表面功函数的主要形式。
