CORROSION INHIBITION STUDIES USING AQUEOUS EXTRACT OF Mallotus oppositifolius ON MILD STEEL IN ACID ENVIRONMENT.

Abstract

The corrosion of metals is a significant environmental issue that needs to be arrested with the aim of protecting the lifespan of metals. In this study, a leaf extract from Mallotus oppositifolius (MOE) was tested as an inhibitor for mild steel corrosion in 0.5 M HCl corrodent solution. Inhibitive effects of (MOE) on mild steel corrosion in 0.5 M HCl solution was investigated using gravimetric method. The corrosion rate of mild steel decreased in the presence of MOE. A gravimetric method was used and the results obtained indicated that the optimum inhibition efficiency was 88.7 % at an extract concentration of 1000 ppm at 323 K. The inhibition efficiency increased with an increase in the MOE concentration and with the period of contact. The effect of temperature, MOE concentration and immersion time on the corrosion rate of mild steel in HCl solution in the absences and presence of MOE was also studied. The inhibition efficiency of MOE increased with increase in temperature up to 323 K and beyond this decrease was noted. The adsorption of the MOE on mild steel is endothermic, spontaneous and is best described by Langmuir adsorption isotherm. Calculated values of free energies of adsorption indicate that the adsorption of MOE on mild steel surface is spontaneous and agrees with the chemisorption mechanism that supports the mechanism of chemisorption.