Experimental and Theoretical Approach for the Corrosion Deceleration of Mild Steel in Hydrochloric Acid Medium by Two Sulfonamide Derivatives

Abstract

In the pursuit to find corrosion inhibitors of superior efficacy, N‐(pyrimidin‐2‐yl)‐4‐[(quinazoline‐4‐yl)amino]benzene‐1‐sulfonamide (PQS) and N‐(4‐methylpyrimidin‐2‐yl)‐4‐[(quinazoline‐4‐yl)amino]benzene‐1‐sulfonamide (MQS) are the two new sulfonamides employed, which have decelerating effect on mild steel (MS) corrosion in a medium 0.5 M HCl and were found to have an efficiency of 98.7 % and 96.8 % respectively (303 K for 40 ppm concentration) deliberated through the electrochemical techniques (PDP and EIS). The inhibitory efficacy relies on the temperature of the solution and inhibitor concentration. PQS had greater stability than MQS at higher temperatures which is indicative in the obtained experimental data. The relative adsorption process was in consonance with the Langmuir adsorption isotherm. The SEM, EDS, FT‐IR, and AFM analysis validated PQS and MQS to form a barrier on MS, opposing corrosion. The potential energy surfaces (PES) scan and a theoretical study for PQS and MQS were probed employing density functional theory (DFT) at B3LYP/6‐311+G(d, p) basis set level that explicated the formation of a complex between the sulfonamides and MS. The corrosion inhibition efficiency of PQS and MQS inferred from experimental and theoretical data comply, making them credible corrosion inhibitors.