Abstract

Saedah R. Al-Mhyawi¹

DOI : http://dx.doi.org/10.13005/ojc/300218

The inhibition efficiency of extract of Garlic on aluminium in hydrochloric acid solutions has been evaluated by weight loss techniques. Values of inhibition efficiency obtained are dependent upon the concentration of inhibitor and temperature. Generally, inhibition was found to increase with inhibitor concentration, half-life, activation energy but decrease with temperature and first-order rate constant at the temperatures studied. Physical adsorption mechanism has been proposed for the inhibition and Langmuir , Temkin adsorption isotherm was obeyed. Garlic is an inhibitor of aluminium corrosion in 0.5  M hydrochloric acid solution.The values of standard free energy of adsorption suggest that the adsorption of inhibitor on aluminium surface occurred by physisorption mechanism. the negative sign of the Free Energy of adsorption indicates that the adsorption of the inhibitors on the aluminum surface was a spontaneous process.the negative values of enthalpy of adsorption (ΔH) suggest that the chemical reaction involved in the adsorption of the inhibitors on the metal surface is an exothermic process, hence increase in the reaction temperature of the medium will decrease the inhibition efficiency.

Corossion; inhibition; Langmur; Temkin adsorption isotherm; half-life; activation energy; free energy.

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