Corrosion Inhibition of Gum Exudates from Acacia malacocephala and Acacia drepanolobium on Mild Steel in Acidic Media

Abstract

The objective of this study was to investigate the corrosion inhibiting properties of gum exudates from Acacia malacocephala and Acacia drepanolobium on mild steel exposed in acidic electrolyte under stationary conditions using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The experiments were conducted in 0.16 M H₂SO₄ electrolyte and the temperature of the electrolyte was varied from 303 K to 323 K without and with the corrosion inhibitors. For the systems at 303 K, inhibition efficiency of over 95% was observed with 600 ppm of gum exudates from A. drepanolobium and 400 ppm of gum exudates from A. malacocephala. When the temperature was increased to 313 K and 323 K, the inhibition efficiency of 600 ppm of gum exudates from A. drepanolobium dropped to 89%, while the inhibition efficiency of 400 ppm of A. malacocephala was reduced to 90%. Thus, temperature was found to have an adverse effect on the inhibition efficiency of the gum exudates. The obtained results indicate that gum exudates from A. drepanolobium and A. malacocephala are good corrosion inhibitors to mild steel under acidic media. Although A. drepanolobium and A. malacocephala are regarded as morphologically similar, the difference in the concentrations of the gum exudates required to achieve maximum corrosion inhibition is one of the justifications to retain them as two distinct species.