Evaluation of 4-amidinophenyl-2,2′-bithiophene and its aza-analogue as novel corrosion inhibitors for CS in acidic media: Experimental and theoretical study

Bichalcophene series namely 4-(2,2′-bithiophene-5-yl) benzamidine (MA-0944) and 6-(2,2′-bithiophene-5-yl) nicotinamidine (MA-0949) were evaluated as corrosion inhibitors for carbon steel (CS) in 1 M HCl using nonelectrochemical and electrochemical techniques. The results revealed that the tested compounds are efficient corrosion inhibitors and their inhibition percentage (η %) reached 98.3% at 18 × 10 − 6 M. The tested compounds are classified as mixed-type inhibitors. The adsorption of the investigated compounds corresponds to Langmuir adsorption isotherm. The surface morphology of the CS surface was analyzed using Attenuated Total Reflectance-infrared spectra (ATR-IR), and Atomic Force Microscopy (AFM). The inhibition property was further elucidated by theoretical approaches; quantum chemical calculation, Natural Bonding Orbital (NBO) analysis, Molecular Dynamic Simulation and Radial Distribution Function (RDF). The theoretical data support the experimental results.