Corrosion inhibition and adsorption behaviour of benzothiazole compounds on mild steel in an acidic environment: Experimental and theoretical approach

To achieve molecular tailoring for strong metal protection, it is essential to have a thorough understanding of the corrosion inhibitor behaviours at the metal–solution interface that are controlled by distinct molecular characteristics. This study examined the corrosion inhibition capability of benzothiazoles derivatives namely-2-((5-amino-1,3,4-thiadiazol-2-yl)thio)-N-(benzothiazol-2-yl)acetamide (ATBA) and 2-((5-acetamido-1,3,4-thiadiazol-2-yl)thio)-N-(benzothiazol-2-yl)acetamide (AATBA) on mild steel alloy exposed in 15 % hydrochloric acid solution. The inhibition performance between the synthesised compounds and the metal surface was investigated by gravimetric as well as electrochemical analysis in 15 % HCl solution. Both inhibitors ATBA and AATBA stand out as excellent corrosion inhibitors with an efficiency of 98.11 % and 97.34 %, respectively, at 200 ppm. Density functional theory (DFT) was used to investigate the electronic properties of the inhibitor molecules. The corrosion inhibitory trend was confirmed by changes in the interaction energy as determined by Monte Carlo simulation. The computation of the Fukui index makes it possible to see how the substituent group affects the relative electron donation and acceptance characteristics of the atoms located at the various locations inside the inhibitor molecule. The adherence of the inhibitors layer and protection of MS surface was confirmed with FESEM, AFM and XPS techniques. The potentiodynamic polarization (PDP) results indicate that the examined compounds are a mixed kind of inhibitor and can control the inhibition mechanism by both anodic and cathodic charge transfer. The adsorption behaviour of the molecules on steel surface follows the Langmuir adsorption isotherm through mixed adsorption as part of the inhibitory process.