Study of thermal stability of epoxy coatings electrodeposited on differentsubstrates

The thermal stability of epoxy coatings electrodeposited on steel, phosphat ized steel, steel electrochemically modified by Zn-Ni alloys and aluminium has been investigated. Epoxy coatings were formed by cathodic electrodeposi tion of epoxy adducts, using a constant voltage method. The rate of hydroge n evolution reaction in the polymer solution on different substrate surface s was determined on Pt rotating disc using a slow sweep voltammetry. The ch aracteristic thermal and thermooxidative degradation temperatures, as the m easure of thermal stability, and activation energies of thermal degradation were determined by thermogravimetric analysis. It has been observed that d ifferent catalytic activities of substrates for H-2? evolution reaction giv e different rise to an increased amount of hydrogen bonds inside the polyme r net and porosity of coating, strongly affecting the thermal and thermooxi dative resistance of the polymeric material. (C) 1999 Elsevier Science Ltd. All rights reserved.