On the use of conducting polymers to improve the resistance against corrosion of paints based on polyurethane resins

This work analyzes the physical properties of several paints and the resistance against corrosion that they impart after being modified by adding a conducting polymer. Five different formulations were selected: four polyurethane resins (two varnish and two aqueous based) and one multicomponent system containing polyester, melamine and cellulose acetobutyrate. The physical properties of the coatings were examined by FTIR, thermal analyses and viscosity measurements. Corrosion resistance of carbon steel coated with these paints was studied by means of accelerated laboratory tests. The results provided by the original formulations and those modified by adding 1% w/w of polypyrrole or poly(3-decylthiophene-2,5-diyl) regioregular were compared. Although the general behavior was irregular, showing dependence with the paint formulation, excellent results were achieved for an aqueous based polyurethane resin modified with polypyrrole. Accelerated immersion experiments in salt and acid solutions showed fast degradation of the film without conducting polymer, while the polymeric film with polypyrrole offered a higher resistance.