Corrosion Inhibition of Mild Steel in Strong Acid Environment by 4-((5,5-dimethyl-3-oxocyclohex-1-en-1-yl)amino)benzenesulfonamide

New sulfanilamide derivative namely 4-((5,5-dimethyl-3-oxocyclohexenyl)amino)benzenesulfonamide (DOBF) was synthesized and the chemical structure was elucidate using Nuclear Magnetic Resonance (NMR) and elemental analysis (CHN). The inhibition effects of a studied DOBF on the corrosion of mild steel in 1 M hydrochloric acid environment were investigated using electrochemical impedance spectroscopy (EIS), weight loss method and scanning electron microscopy (SEM). The synthesized inhibitor concentrations were 0.1 mM to 0.5 mM and the temperatures ranging from 303-333 K. Results showed that the inhibition occurs through adsorption of the inhibitor molecules on the metal surface. Electrochemical and weight loss techniques revealed that the tested DOBF act as superior inhibitor for acidic corrosion of mild steel and the efficiency increase with increasing concentrations. EIS results revealed that DOBF demonstrate the highest inhibition efficiency of 93.70 %, at a concentration of 0.5 mM. The adsorption of the investigated inhibitor obeys Langmuir's adsorption isotherm. Different thermodynamic parameters have been calculated and discussed. SEM confirmed the formation of a protective film on the surface. The investigated techniques are in good agreement to establish the using DOBF as corrosion inhibitor for mild steel in strong acid environment. It was found that the corrosion inhibition performance depends on the concentration of the DOBF and the solution temperature. Quantum chemical calculations have been done to correlate the electronic characteristics of the compounds with the corrosive inhibitive impact. The quantum calculations such as the HOMO, LUMO, energy gap (ΔE), atomic charges, dipole moment (μ), electron affinity (A), chemical hardness (η), softness (σ) electronegativity (χ), ionization potential (I), and fraction of electrons transferred (∆N), were used to explain the mechanism of inhibition of DOBF molecules on the mild steel surface. Experimental and theoretical results are in good agreement.