On the evaluation of metal-corrosion inhibitor interactions by adsorption isotherms

Aiming to provide a wide perspective on metal-corrosion inhibition modeling the classical, modern and the so-called functional surface dependency adsorption isotherms were reviewed in order to clarify the working frameworks from either physical or chemical bonding continuous that best apply on various electro-chemical circumstances. This way, from the fashioned Langmuir isotherm, to its multi-scalar versions: the Freundlich isotherm to Temkin isotherm suitable for heterogeneous metal surfaces have been discussed. As such, the Flory - Huggins and Bockris - Swinkels isotherms allow the evaluation of the number of adsorbed water molecules replaced by one inhibitor molecule. The El-Awady isotherm is highlighting the number of layers of inhibitor molecules from the metal-solution interface. The Volmer isotherm is accounting for the possibility of adsorbate molecules to move from one adsorption site to another, in the absence of any lateral effects. The Dubinin-Radushkevich isotherm recently used in corrosion studies models the corrosion inhibitors via the adsorption energy Eads. All of presently considered isotherms may contribute in better characterizing nano-materials and surface processes via molecular electrochemistry and metal-ionic interaction on a hierarchical inclusive analytical framework.