Inhibitory Potential of N-Methyl Formanilide on Mild Steel Corrosion in Sulfuric Acid: Quantum Chemical and Experimental Perspectives

Abstract

Technological progress has led to increased use of metals and alloys such as aluminum, brass, bronze and mild steel. While mild steel is favoured for its availability, low cost and excellent mechanical properties, it is prone to corrosion. This study aims to reduce the corrosion of mild steel in sulfuric acid using N-methyl formanilide (NMF) as an inhibitor. The effectiveness of NMF was evaluated using gravimetric method (weight loss) and electrochemical impedance spectroscopy (EIS). Surface analyses were conducted using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The study examined the performance of NMF at different temperatures (298 K to 338 K) and varying inhibitor concentrations. The results indicated that the percentage inhibition efficiency (%IE) of NMF increased with higher concentration but decreased with temperature. The NMF formed a protective layer on mild steel through physical adsorption, which was confirmed by El-Awady adsorption isotherm and comparing it with other adsorption models. The kinetic and thermodynamic studies were also performed, with activation energy (Ea) and adsorption free energy (ΔG°ads) being calculated. These findings were further validated using the AM1 quantum mechanical method, revealing the promising results for the investigation.