Electrochemical preparation of composite coatings of 3,4-etylenodioxythiophene (EDOT) and 4-(pyrrole-1-yl) benzoic acid (PyBA) with heteropolyanions

•The composite SiMo12-PEDOT/PyBA coatings on carbon and steel substrates were investigated.•The coatings have exhibited very good adhesion to the substrate.•The coatings are capable of largely blocking the access of chlorides anions.

The possibility of incorporating 4-(pyrrole-1-yl) benzoic acid, (PyBA), and heteropolyacids (SiMo12) during the electrodeposition of poly (3,4-ethylenedioxythiophene), PEDOT, is demonstrated in the paper. The formed novel composite material was applied on the electrode surface as a moderately thin (ca. 0.9–1 μm thick) PEDOT/PyBA/SiMo12 coating. The physicochemical identity of our composite coating was established with the use of electrochemical, spectroscopic, and microscopic techniques. The fact that carboxylate-containing PyBA units link with positively charged and PEDOT structures tend to improve the overall stability and adherence of composite coatings to glassy carbon and stainless steel. The PEDOT/PyBA composite serves as a stable host matrix for large negatively charged silicium heteropolymolybdates inorganic species. Consequently, due to the formation of denser polymeric structures and due to the existence of electrostatic repulsion effects, the large polyanion-containing composite coatings are capable of blocking the access of smaller pitting-causing anions (chlorides) to the surface of stainless steel.

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