Comparative analysis of anti-corrosive performance: Azure C dye vs. alternative Azure dyes on mild steel in 1 N HCl at elevated temperatures

Organic derivatives and dyes represent a promising and efficient class of corrosion inhibitors, demonstrating considerable potential in fulfilling the criteria for utilization as corrosion inhibitors. In the present study, the anti-corrosive impact of some Thiazines dyes: Azure A (D-1), Azure B (D-2) and Azure C (D-3), has shown a decelerative effect on mild steel in 1 N HCl environment and was investigated using experimental {Weight loss (WL), Electrochemical method and Atomic Force Microscope (AFM)} and theoretical {Density Functional Theory (DFT)} studies. It was found to have an efficiency in the order of D-3 (98.09 %) > D-1 (89.94 %) > D-2 (76.44 %) at elevated temperatures (338 K for 100 ppm concentration) deliberated through WL method. D-3 had greater stability than D-1 and D-2 at elevated temperatures which is indicative in the obtained experimental data. As examined via electrochemical and WL analysis, the cathodic type of inhibition mechanism and adsorption isotherm viz. Langmuir, Temkin and El-Awady were followed by all three dyes. Results of surface analysis and thickness of deposited layer by AFM agreed with other experimental outputs. A theoretical study for these thiazine dyes was probed employing DFT that illustrated the formation of a complex among the dyes and mild steel. The corrosion inhibition efficacy of dyes, as deduced from both experimental and theoretical data, aligns cohesively, thereby establishing a comparatively durable monolayer at the mild steel/medium interface, preventing steel deterioration in a specified range of temperatures.