Schiff’s base with center of symmetry as an effective corrosion inhibitor for mild steel in acid medium: Electrochemical & simulation studies

Abstract

Green and efficient corrosion inhibitors have received widespread attention from various disciplines due to their wide application in petrochemical and other fields. However, because of its inability to fully understand the corrosion inhibition mechanism, the understanding of corrosion inhibition performance is limited. In this work, we synthesized a Schiff base (1, 2−1H-Benzoimidazol-2-yl)-(1, 2-diphenyl-ethylidene)-amine) (BDEA) with centre of symmetry structure by 2-aminobenzimidazole and benzyl. The central symmetric distribution of the heteroatoms has a higher coordination effect, thus, the adsorption performance has been outstanding. Characterization of synthesized compound was done using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis. The corrosion inhibition property of the synthesized Schiff base on X80 steel was determined using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SECM) analysis in 1 M HCl medium. Surface analyses of the alloy samples were performed using atomic force microscopy (AFM) analysis and contact angle measurement. BDEA can effectively protect X80 steel corrosion in 1 M HCl medium and the maximum efficiency obtained was 94.26 %. The surface analysis further proved that morphology of the metal surface was more protected in the presence of BDEA. In addition, the production of the reaction between BDEA and Fe3+ were studied by UV–vis spectrum analysis, and the mechanism was deliberated. The study of SECM showed that BDEA could adsorb both active and non-active regions on the metal surface at the same time. DFT studies suggested that the inhibition efficiency of its neutral as well as protonated form followed the order of η(protonated form) >η(neutral form) using DFT-based quantum chemical calculations. Besides, the degradation of BDEA showed that temperature had a significant effect on the degradation rate of BDEA using total organic carbon (TOC) analysis. Thermogravimetric analysis (TGA) indicated BDEA had admirable thermal stability. The influence of molecular behavior on corrosion inhibition performance is revealed from the perspective of structural characteristics. This work provides strong evidence for revealing the effect of structure on corrosion inhibition mechanism.