Polypyrrole coatings as a treatment for zinc-coated steel surfaces against corrosion

A single-step electropolymerization of pyrrole on zinc-coated steel electrodes in aqueous medium was investigated under several techniques (potentiodynamic, galvanostatic and potentiostatic modes) by using carboxylate salts, such as the citrate, the succinate, the oxalate, the malate and the tartrate. Adherent and homogeneous PPy coatings were obtained only with tartrate counter-ions. The corrosion behaviour of zinc-coated steel electrodes electrochemical modified by PPy films were estimated by open circuit potential and DC polarization in NaCl, HCl and H2SO4 aggressive solutions. The obtained results show that the PPy coatings increase the corrosion potential and reduce the corrosion current. The salt spray test results show that the PPy coating prepared under ultrasonic waves is more resistant than those obtained in normal conditions. (C) 2004 Elsevier Ltd. All rights reserved.