POLYOXYPHENYLENE COATINGS BY ANODIC ELECTROPOLYMERIZATION OF PHENOLS IN THE PRESENCE OF AMMONIUM-COMPOUNDS

Amine-free polyoxyphenylene coatings were obtained on mild steel anodes by electropolymerizing phenol/2-allylphenol mixtures dissolved in hydroalcoholic solutions containing ammonium compounds. Ammonia allowed polymer growth up to thicknesses of ~15 µm in 10 min of constant voltage electrolysis. When (NH4)2S was selected as the ammonium compound, coatings were found to contain sulfur and to display remarkable barrier properties: negligible penetration of the electrolyte in the coating could be tested by ac impedance experiments within 1 month’s exposure to 0.5M NaCl. Electropolymerization of phenols in ammonia solutions was also achieved on Zn but, since monomer oxidation was always paralleled by metal dissolution, highly porous, poorly protecting coatings were obtained. © 1990, The Electrochemical Society, Inc. All rights reserved.