H ALIDE ION AND METHANOLIC EXTRACT OF IRVINGIA GABONESIS AS AN E NHANCED CORROSION INHIBITORY AGENT ON ALUMINIUM IN HCl

Abstract

The in hibitory efficiencies of methanolic leaf extract of Irvingia gabonensis and the role of a halide ion as an enhancement on the inhibition of aluminium corrosion in HCl medium were studied at varying acid concentrations of 0.01M , 0.05M, 0.1M und er the influence of 3% NaCl. Result of the studies carried out by weight loss techni que showed that I. gabonensis is highly an efficient inhibitor for the corrosion of al umimium in HCl acid environment and its inhibitory efficiencies increases with respect to the time of exposure.. It was observed from the study that in the absence o f the plant extracts, the weight loss increases rapidly indicating an increase in corrosi on rate from 0.003g to 0.026g as acid concentration was increased from 0.01M to 0.1M . Conversely, when the plant extract was introduced, there were remarkable decrease in weight loss from 0.001g at 0.01M of HCl to 0.021g at 0.1M , showing a decrea se in corrosion of the metal. Experimental data proved that the highest corrosion rates w ere observed at the highest acid strength pointing that at a concentration of 0.1M H Cl, 19% efficiency was attained and a maximum efficiency of 67% was obtained at 0.01MHCl showing a correlation between concentration and inhibition of metal. It was also revealed that the inhibitory efficiency of I. gabonensis in HCl medium was magnif icently increased when a salt of halide ion was introduced showing a weight loss of 0.01g through 0.003g as acid strength increased from 0.01M to 0.1M. This could be attributed to that the fact that halide ion facilitates the adsorption of organic cat ions during metal corrosion by forming intermediate bridges between the metal surface and the positive end of the organic inhibitor and this forms a protective hydrophi lic film on the metal surface which provided a barrier to the dissolution of the metal into the acid medium.