Electropolymerization of pyrrole on mild steel for corrosion protection

Polypyrrole (PPy) can be synthesized by either chemical or electrochemical methods. Electrochemical methods (electropolymerization) usually give higher PPy conductivity than the chemical methods. However, the electropolymerization of pyrrole on oxidizable metals such as mild steel is difficult because the metallic electrode undergoes strong dissolution before oxidation potential of the monomer (pyrrole) is reached. Recently, a few electrochemical methods have been proposed to polymerize pyrrole on various steel substrate successfully. In this work, these methods are evaluated to select the best one, from the corrosion protection point of view. Subsequently, a parametric study was undertaken on the selected method to study the effect of electropolymerization parameters namely; applied current density, electrolyte pH and temperature.; Among the tested methods, a method that uses oxalic acid as electrolyte showed the most adherent deposition of polypyrrole on mild steel. The parametric study on this method shows that increasing the current density can enhance the deposition but the surface becomes rough. The time needed for passivating the steel surface (induction time) decreases with increased applied current density while the electropolymerization potential increases with current density. (Abstract shortened by UMI.)...