Study of Corrosion Behavior of N'-acetyl-4-pyrrol-1-ylbenzohydrazide for Low-Carbon Steel in the Acid Environment: Experimental, Adsorption Mechanism, Surface Investigation, and DFT Studies

New corrosion inhibitors, namely N'-acetyl-4-pyrrol-1-ylbenzohydrazide (NAPB), were synthesized by the reaction of 4-pyrrol-1-ylbenzohydrazide with acetic anhydride. NAPB was characterized by FTIR and NMR spectroscopy. Weight loss measurement was used to evaluate the corrosion inhibition of Low-carbon steel in a 1 M hydrochloric acid medium. The inhibition efficiency (IE%) increased as NAPB concentration increases and decreases as the solution temperature increases. The inhibition efficiency reached 94.6 % at the optimum concentration (500 ppm) of NAPB. The scanning electron microscopy technique proved the formation of a protective layer from NAPB molecules as corrosion inhibitors on the Low-carbon steel surface. The adsorption isotherm of NAPB molecules on the surface of Low-carbon steel was confirmed to follow the Langmuir adsorption isotherm. Further, through quantum chemical calculations using density functional theory (DFT), the importance of inhibition performance and molecular structure of an inhibitor has been theoretically investigated. Both experimental and theoretical findings are consistent with one another.