BENIGN APPROACH OF CANTHIUM PARVIFLORUM AS A BIOINHIBITOR FOR MILD STEEL CORROSION IN 0.5 M H2SO4 MEDIUM

Canthium parviflorum leaf extract (CPLE) was utilized for corrosion prevention against mild steel (MS) in 0.5 mol L-1 H2SO4 test medium. Standard corrosion measurement techniques (gravimetric and electrochemical) were employed for this purpose. Gravimetric tests clearly confirmed that the prepared CPLE efficiently performs as corrosion inhibitor. Potentiodynamic polarization measurements (PPM) and electrochemical impedance spectroscopy (EIS) measurements were performed in order to analyze the charge transfer process of CPLE. Polarization curves indicate that CPLE acts through mixed mode inhibition. Impedance study reveals that the CPLE additives enhances the charge transfer resistance values and conversely decreases values of double layer capacitance. Scanning electron microscopy (SEM), Ultraviolet-Visible (UV-Vis) spectroscopy analysis and Fourier-Transform Infrared spectroscopy (FTIR) were done to confirm the Fe-CPLE complex formation on MS. The effect of temperature reveals that the inhibition efficiency increases with decrease in temperature and increase in concentration of CPLE (maximum of 4 mg L-1). The adsorption of CPLE shows that it obeys Langmuir's isotherm model with free energy of adsorption, Delta G(ads) = 1.76 kJ mol(-1). A suitable adsorption model is also proposed.