Factors affecting acid-base stability of the interface between polyaniline emeraldine salt and oxide covered metal

Abstract

Coatings containing polyaniline emeraldine salt (ES) or base (EB) dispersed in organic binder were applied to Al, Fe, Zn, and Mg substrates and held in air at 93% RH. EB coatings produce neither oxide growth nor increase in open circuit potential (Eoc). ES coatings induce oxide growth. They also increase Eoc to ca. 0.5 V vs SHE on Al and Fe, but not on Zn and Mg. Findings are consistent with metal oxides with acidic cations (pKa1 ≫ 5.5) being stable in contact with ES (pKa 5.5), while those with less acidic cations (pKa1 ≫ 5.5) deprotonate ES to electroinactive EB. © 2005 The Electrochemical Society. All right reserved.