Ethanol extract of Terminalia catappa as a green inhibitor for the corrosion of mild steel in H_2SO_4

摘要

The inhibitive and adsorption properties of ethanol extract of Terminalia catappa for the corrosion of mild steel in H_2SO_4 were investigated using weight loss, hydrogen evolution, and infra red methods of monitoring corrosion. Ethanol extract of T. catappa is a good adsorption inhibitor for the corrosion of mild steel in H_2SO_4. The inhibition efficiency of the inhibitor increases with increasing concentration but decreases with increasing temperature. The inhibition potential of ethanol extract of T. catappa is attributed to the presence of saponnin, tannin, phlobatin, anthraquinone, cardiac glycosides, flavanoid, terpene, and alkaloid in the extract. The adsorption of the inhibitor on mild steel surface is exothermic, spontaneous and is best described by Langmuir adsorption model. From the calculated values of activation energy, free energy of adsorption and the trend in the variation of inhibition efficiency with temperature, the mechanism of adsorption of the inhibitor is physical adsorption.