On the Use of the Langmuir and Other Adsorption Isotherms in Corrosion Inhibition

In corrosion inhibition studies, the standard adsorption Gibbs free energy is often estimated via the linear regression of the Langmuir-like c/θ = 1/K + mc equation, where m is the slope. Herein, a theoretical basis for this equation is established, and it is demonstrated to be an effective equation that can decently describe various adsorption models and provide relatively accurate estimates for standard adsorption free energy, provided surface coverages are reliably determined experimentally. However, any significant deviation from the slope of 1 signals non-Langmuir adsorption due to inter-adsorbate interactions, multi-site adsorption, or surface heterogeneity.