Corrosion inhibition of mild steel by gum exudates from acacia malacocephala and acacia drepanolobium in acidic media

This dissertation reports on the corrosion inhibiting properties of gum exudates from Acacia malacocephala and Acacia drepanolobium on mild steel in acidic media under both stationary and dynamic conditions. Two electrochemical techniques (Electrochemical Impedance spectroscopy and Potentiodynamic Polarization measurement) were used. 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 inhibitor. For the stationary 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 effeciency 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. For the dynamic systems at 303 K, inhibition efficiency of about 90% was observed with both 400 ppm of the gum exudates from A. drepanolobium and 300 ppm of exudates from A. malacocephala. The obtained results indicate that gum exudates from A. drepanolobium and A. malacocephala show very good corrosion inhibition towards mild steel under acidic media. Also observed is that 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 justifies to retain them as two distinct species.