ABSTRACT
Extracts from the leaves of three plants namely; guava (Psidiumguajava: Fem- Myrtaceae), banana (Musa species: Fem-Musaceae) and almond leaves (Prunusamygdamus: fem- Rosaceae) were subjected to physico-chemical, phytochemical screening and corrosion test using gravimetric measurement with a low carbon steel flat bar coupon. The corrosion inhibition mechanism of the three plants extract on the low carbon steel surface in 0.5M HCl and H2SO4 acid at different temperatures (30-60oC) show that the inhibition efficiency (IE) increases with increase in concentration of the inhibitor (250ppm-1000ppm) but decreases with increase in temperature (303K -333K) for all the three inhibitors throughout the test period, indicating a physisorption of extract on the carbon steel surface. As the concentration of the inhibitors increases, higher values of the positive activation energy (Ea) ranging from 45.509 kJ/mol - 56.051 kJ/mol indicating physisorption adsorption and positive enthalpy of activation (42.869 kJ/mol - 53.413 kJ/mol) indicating the endothermic nature of adsorption of the inhibitor on low carbon steel were obtained. The values of free energy of adsorption were found to increase (26.624 kJ/mol -29.859 kJ/mol) with increasedin temperature indicating a comprehensiveadsorption (a combination of physisorption and chemisorption) of the inhibitors on the low carbon steel surface. The adsorption on the low carbon steel surface agrees the Langmuir adsorption isotherm. The inhibition efficiency of the three extracts were above 50% in both media with guava extract having the overall best performance of 77.79% in HCl while banana extract with 77.25% in H2SO4 solution respectively