Application of a polythiophene derivative as anticorrosive additive for paints

This work compares the resistance against marine corrosion of several paints before and after being modified by adding a conducting polymer derived from polythiophene. The selected paints, which were applied to the naval steel St F111, are primers specially indicated for protection in marine environments. The physical properties of both the unmodified and the modified paints were characterized using viscosity measurements, FTIR and thermal analyses, and mechanical properties evaluations. Results show that the addition of a low concentration (0.2%, w/w) of poly(3-decylthiophene-2,5-diyl)-regioregular greatly improve the performance of the epoxy-based resin. Thus, laboratory immersion tests in NaCl solution showed irregular surface and composition degradations of the film without conducting polymer, after 3 days, while the polymeric film with the conducting polymer did not suffer any change until 30 days. The effects of the degradation on the coating surfaces were analysed using both optical and scanning electron microscopy (SEM).