Surfactants and Biosurfactants as Green Corrosion Inhibitors

Abstract

Surfactants are surface active agents that contain both hydrophilic and hydrophobic moieties. They are widely used for different industrial, pharmaceutical and industrial applications including as corrosion inhibitors. Obviously, these compounds become effective by adsorbing on the metal surface using their hydrophilic polar heads. They can be classified into various classes including cationic-, anion-, zwitterionic- and non-ionic-, bolaform and gemini-type depending upon the nature and number of hydrophilic head and hydrophobic hydrocarbon chain. Generally, their adsorption follows the Langmuir adsorption isotherm model. They behave as mixed- and interface-type corrosion inhibitors as their presence affects the nature of the anodic and cathodic Tafel reactions without shifting the corrosion potential significantly. Surface investigations are widely used to support the adsorption mechanism of corrosion prevention by these compounds. Computational based studies especially DFT, MDS and MCS are also used to describe the mode and nature of interaction between surfactants/biosurfactants and the metallic surface.