Considering the concept of synergism in corrosion inhibition

Synergism in corrosion inhibition and how to best quantify it is explored conceptually. In the equation for the synergistic parameter, the mixture's inhibition efficiency is evaluated against a threshold inhibition efficiency based on the performance of pure compounds. However, the choice for the threshold value is not unique. In the literature, the threshold of Aramaki–Hackerman is usually used. Herein, several other reasonable choices are developed, which are based on (i) the Langmuir adsorption model, (ii) the requirement that a mixture's inhibition efficiency is higher than the highest inhibition efficiency of pure compounds, or (iii) that corrosion resistance in a mixture is higher than the sum of resistances in pure compounds. The presented synergistic models are also extended to multi-component mixtures.