FORMATION OF POLYPYRROLE COATINGS ONTO LOW-CARBON STEEL BY ELECTROCHEMICAL PROCESS

Thin polypyrrole coatings (similar to 10 mu m thick) were formed on lo w carbon steel by an aqueous constant current electrochemical polymeri zation using oxalic acid as the electrolyte. The amount of polypyrrole coatings formed on steel increased with the applied current and monom er concentration. No significant change in the electropolymerization o f pyrrole occurred as a result of increased electrolyte concentration. The induction time for electropolymerization decreased significantly with current density but was unaffected by the initial monomer and ele ctrolyte concentration. The electropolymerization potential of pyrrole increased with increased current density (Cd), i.e., Ep = 0.62 + 0.41 [Cd], and decreased exponentially with increased monomer and electrol yte concentration, Ep = E-0 exp(-[M]). Scanning electron microscopy (S EM) showed that the microstructure of the polypyrrole coatings formed on steel was dependent on the current density to the extent that smoot her and more uniform coatings are formed at low current density. (C) 1 997 John Wiley & Sons, Inc.