Determining Gibbs energies of adsorption from corrosion inhibition efficiencies: Is it a reliable approach?

Abstract The common practice of using inhibition efficiency (η%) to determine the standard Gibbs energy of adsorption ( ΔG ads o ) for a corrosion inhibitor in acidic solution is evaluated. It is demonstrated that the typical assumption that η% is a good proxy for fractional surface coverage (θ) is not necessarily valid. Consequently, the accuracy of the ΔG ads o value obtained from such data is doubtful. Moreover, it is argued that even a more direct measurement of θ may still not allow one to extract an accurate estimate of ΔG ads o .