Adsorption and corrosion inhibition properties of thymol

Abstract

On the basis of electrocapillary and differential capacitance measurements it was established that thymol from acid solutions was adsorbed on a mercury electrode. The shape of the thymol adsorption isotherm, the positive value of the attraction constanta and the position of the minimum of the∂ Inc/∂θ vsθ dependence (wherec is thymol concentration andθ is electrode coverage) indicated the applicability of the Frumkin equation. The characteristics of thymol as a corrosion inhibitor were studied by observing the dissolution of aluminium and zinc in hydrochloric acid with and without thymol addition. The values of the reaction numbers (RN) plotted against thymol concentration were compared with the adsorption curves. The analysis of the results, i.e. the comparison of theRN(c) andθ(c) curves for the liquid and solid metal electrodes and the difference between theRN(c) curves for aluminium and zinc, indicated a different adsorption mechanism and also a different corrosion inhibition efficiency by thymol for aluminium and zinc.