Jatropha podagrica stem bark extract as a novel green corrosion inhibitor for carbon steel in acid medium: A combined experimental and computational explorations

Abstract

The inhibition efficacy of a novel green corrosion inhibitor based on Jatropha podagrica stem bark extract (JPSE) toward carbon steel (CS) corrosion in 0.5 M H₂SO₄ solution was explored by integrated experimental and computational studies. The inhibition behavior was probed using weight loss analysis, potentiodynamic polarization (PDP) test, electrochemical impedance spectroscopy (EIS) and surface analysis techniques. In addition, the adsorption process between JPSE compounds and iron atom was theoretically examined by using quantum chemical calculations and molecular dynamics (MD) simulations. The experimental results revealed that 600 mg L^-1 JPSE protected the CS surface by ~87%.  The polarization tests revealed that the JPSE acted as a mixed type inhibitor with dominant effect on the cathodic reactions restriction. The EIS analysis showed that the increase of JPSE concentration led to the significant increment of charge transfer resistance. Surface analysis via SEM clearly proved that JPSE adsorption on the CS surface remarkably reduced its dissolution rate and resulted in a smooth morphology. UV–visible analysis evidenced the formation of a complex between the functional groups of the considered inhibitor and metal ions. The theoretical results demonstrated the adsorption of JPSE constituents on the CS substrate in parallel mode.