Evaluation of an environmentally friendly anticorrosive pigment for alkyd primer

• Published in: Progress in organic coatings 2012-04, Vol.73 (4), p.321-329
• Main Authors: Martí, Mireia, Fabregat, Georgina, Azambuja, Denise S., Alemán, Carlos, Armelin, Elaine
• Format: Article
• Language: English
• Subjects: Alkyd primer; Corrosion and anti-corrosives; Corrosion resistance; Corrosió i anticorrosius; Electrochemical impedance spectroscopy; Enginyeria química; Espectroscòpia d'impedància; Polyaniline; Polythiophene; Àrees temàtiques de la UPC
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2011.10.017

► Three new alkyd coatings, based on conducting polymers as eco-friendly anticorrosive pigments, were prepared. ► A polythiophene derivative, synthesized by chemical oxidative polymerization, provided the best protection compared to polyaniline and zinc phosphate additives. ► A very low concentration (less than 1.5wt.%) is required to provide efficient protection. An alkyd formulation containing zinc phosphate (10wt.%) was prepared and subsequently modified replacing the latter anticorrosive additive by a very low concentration of conducting polymer. Specifically, three modified paints, which contain polyaniline emeraldine base (undoped form), polyaniline emeraldine salt (doped form) and an eco-friendly polythiophene derivative (partially oxidized), were formulated. The properties and corrosion resistance of the four alkyd coatings have been characterized. Among the three modified paints, the one containing polythiophene shows the best adherence and the highest corrosion resistance. This has been attributed to the fact that the miscibility of the polythiophene derivative with the alkyd formulation is better than that of polyaniline. Furthermore, accelerated corrosion assays and electrochemical impedance spectroscopy measurements revealed that the corrosion resistance of the paint with polythiophene is several orders of magnitude higher than that with zinc phosphate. The polythiophene derivative has been found to induce the formation of a passivating and well-adhered layer between the coating and the surface, preventing the access of chloride anions and oxygen to the substrate.