Anticorrosive Electroactive Castor Oil-Based Polyurethane Coatings: Preparation and Properties

In the present workelectroactivepolyurethane coating was prepared via aringopening reactionof epoxy-terminated castor oil based polyurethane prepolymers with theappropriate amount of amine terminated aniline trimer oligomer (AT). Also, thenon-electroactivepolyurethane coating was prepared via replacing of AT via 1, 6 hexamethylene diamine (HDA) as acuring agent. The chemical structure of prepared coatingswas fully characterized by aconventional spectroscopic method and their physicochemical properties including chemical resistance, hardness and adhesion strength were alsoevaluated.The electroactivity behavior of the prepared coatings was confirmed by cyclic voltammetry technique. The corrosion protection properties of the both electroactive and non-electroactivecoatings on mild steel (MS) were measured by Tafel polarization technique and electrochemical impedance spectroscopy (EIS). According to the Tafelresult, aconsiderablereduction in corrosion current (Icorr) and amore positive shift in corrosion potential (Ecorr) were detected forelectroactive polyurethanecoated MSin comparison tothose bare and as well as non-electroactive polyurethane coated MS. Also, the EIS result indicated the higher pore resistance (Rp) valuesand consequently higher corrosion protection for electroactive coating in comparison to non-electroactive polyurethane coated MS. The higher chemical resistance, hardness, and adhesion strength were recorded for electroactive polyurethane coating. Based on recorded data, it was revealed that the prepared electroactive polyurethanecoatings not only could prevent the arrival of corrosion spices to the metal surface like a hydrophobicpolymer coatingbut alsocould enhance corrosion protection efficiency via redox reactions of their oligoaniline moieties with the metal surface.