The role of adhesion promoters, copper oxidation, and thermal aging in the adhesion mechanism of enamel on copper winding wires is investigated. Evidence is presented on the predominant role of the copper oxide at the interface in the wire-enamel adhesion phenomena. The oxidation process and the copper oxides stability at the interface are seen to strongly depend upon the thermal aging of the wire and the nature of both the enamel and the promoter. Atomic force and scanning electron microscopy analyses show that so-called promoters act more efficiently as corrosion inhibitors than as adhesion enhancers. (C) 2003 Wiley Periodicals, Inc.