Electrochemical Investigation of the Corrosion Inhibiting Effect of Organic Paints Doped with Benzotriazole Coated on Steel Substrates

A detailed electrochemical investigation of two different alkyd paints which were mechanically mixed with benzotriazole (BTA), was carried out with the purpose of enhancing their anti-corrosion properties and better understand the corrosion mechanism. Additionally, in some cases pretreatment was performed with a gallic acid-based mixture prior the paints application. A comparison is drawn between the paint systems with and without inhibitor and pretreatment, for which the electrochemical properties are characterized by electrochemical impedance spectroscopy (EIS) and Potentiodynamic polarization. Various equivalent electric circuits were proposed to describe the behavior of the coated steel and the kinetic parameters of the corrosion process were determined by experimental EIS data simulation. The corrosion behavior of damaged (scratched) coatings was also investigated and compared to that of the undamaged, painted mild steel substrates. The study puts in evidence the beneficial effect of the BTA incorporated in both paint systems, the pretreatment and their cumulated effect to stand in the increase in the corrosion resistance of the coatings. The presence of the modifying agents caused an increased resistance even in the scratched samples. Furthermore, a short term self-repairing effect was noticed due to both the corrosion inhibitor and pretreatment.