The paper considers the problem of solid-phase oxidation for cases of polyethylene coatings applied onto active (copper) and passive (aluminum) substrates. Oxidation of PE coatings on copper, unlike that of PE coatings on aluminum, is shown to develop in two stages separated by a time period of autoinhibition. During this time period the concentration of carboxyl groups does not in fact change. In a similar manner copper-containing compounds accumulate in the coating, which fact supports the relation between metal transfer and polymer oxidation processes.