Inhibition of mild steel corrosion in acid media using tephrosia purpurea and pongamia pinnata a green approach to corrosion mitigation

Abstract

newlineCorrosion inhibition characteristics of methanol extract of Tephrosia purpurea and Pongamia pinnata leaves on mild steel in 1N HCl and 1N H2SO4 were investigated in this present work The leaf extract of Tephrosia purpurea and Pongamia pinnata were prepared by Soxhlet extraction method using methanol as solvent Characterization of leaf extract of Tephrosia purpurea and Pongamia pinnata were carried out using UV Visible UV Fourier Transform Infrared Spectroscopy FT-IR Nuclear Magnetic Resonance Spectroscopy NMR and Gas Chromatography-Mass Spectroscopy GCMS analysis The corrosion studies were carried out using weight loss measurements electrochemical methods such as potentiodynamic polarization method and Electrochemical Impedance Spectroscopy EIS technique Weight loss measurements were carried out at different temperatures, with varying immersion time and varying concentrations of inhibitors The weight loss measurements showed that the inhibition efficiency was increased with increase in concentration of inhibitors up to 300 ppm and slightly decreased with further increase of the inhibitor concentration This indicates that 300 ppm could be considered as the optimum inhibitor concentration Polarization results revealed that the corrosion current density icorr values decreased as the leaf extracts concentration increased and from ba and bc values it has been found that both the inhibitors acted as mixed type inhibitors Impedance method indicated that the Rct values increased but Cdl values decreased with increase in inhibitor concentration EIS measurements showed that the corrosion process was controlled by single charge transfer mechanism The results obtained from EIS studies are in good agreement with the results obtained from weight loss and polarization methods.