Study of thermal stability of epoxy coatings electrodeposited on different substrates

Abstract

The thermal stability of epoxy coatings electrodeposited on steel, phosphatized steel, steel electrochemically modified by Zn-Ni alloys and aluminium has been investigated. Epoxy coatings were formed by cathodic electrodeposition of epoxy adducts, using a constant voltage method. The rate of hydrogen evolution reaction in the polymer solution on different substrate surfaces was determined on Pt rotating disc using a slow sweep voltammetry. The characteristic thermal and thermooxidative degradation temperatures, as the measure of thermal stability, and activation energies of thermal degradation were determined by thermogravimetric analysis. It has been observed that different catalytic activities of substrates for H-2? evolution reaction give different rise to an increased amount of hydrogen bonds inside the polymer net and porosity of coating, strongly affecting the thermal and thermooxidative resistance of the polymeric material. (C) 1999 Elsevier Science Ltd. All rights reserved.