INHIBITION EFFECT OF ADMIXED CITRUS PARADISE AND CYMBOPOGON OIL DISTILLATES ON THE CORROSION RESISTANCE MILD STEEL IN DILUTE ACID ELECTROLYTES
Abstract
Corrosion suppression effect of the combination of citrus paradise and cymbopogon oil distillates on mild steel (MS) in 0.5M H2SO4 and HCl solution was studied by potentiodynamic polarization, open circuit potential measurement, optical microscopy characterization, and ATF-FTIR spectroscopy. The distillates performed adequately in both acids at all concentrations considered with average inhibition efficiency above 90%. Corrosion rate of the non-inhibited steel at 7.690 and 2.819mm/y from both acids were substantially reduced to values between 0.465 and 0.466mm/y in H2SO4 while the values in HCl are 0.081 and 0.034mm/y. The distillates exhibit mixed type inhibition performance in both acids. However, polarization plots displayed cathodic passivation effect at higher distillate concentration in H2SO4 while cathodic-anodic passivation plots were observed at all distillate concentrations in HCl solution. Corrosion potential plots from open circuit measurement at specific distillate concentrations were significantly electropositive compared to the non-inhibited steel which was electronegative. Inhibition effect of the distillates occurred through chemisorption adsorption mechanism with Gibbs free energy values greater than −40KJ/Mol, in agreement with Langmuir isotherm model. Optical images of the non-inhibited steel displayed a severely degraded exterior which significantly contrast the protected exterior of the inhibited steel.
