Chapter22 - Oleochemicals as corrosion inhibitors

Abstract

Because of their environmental friendly nature and huge availability at relatively low cost, oleochemicals are extensively used as corrosion inhibitors for numerous metal/electrolyte systems. Generally, these compounds become effective by adsorbing on the metallic surface following through the Langmuir adsorption isotherm model. Oleochemicals form a hydrophobic surface film at the interface of metal and electrolyte in which polar/hydrophilic site(s) oriented towards the metallic surface and non-polar/ hydrophobic site(s) directed towards electrolyte. A proper combination of hydrophilicity and hydrophobicity is essential for effective anticorrosive effectiveness. Obviously, a very high magnitude of hydrophobicity adversely affects the inhibition potential of oleochemicals by reducing their solubility in the polar electrolytes. Outcomes of electrochemical studies suggest the oleochemicals mostly act as mixed- and interface-type corrosion inhibitors and they become effective by adsorbing at the interface of metal and electrolyte. Various suitably modified oleochemicals have also been tested as corrosion inhibitors for different metal/electrolyte systems. Oleochemicals and their derivatives act as mixed-type corrosion inhibitors. Oleochemicals interact with the metallic surface using a donor-acceptor mechanism (DFT) and acquire flat orientation (MDS or MCS).