The degraded interface layer between rubber and galvanized steel bonded with HRH (Hisile-Resorcinol-Hexamethylenetetramine) direct curing adhesion system was observed. After aging at 160 C° for 150 min with the hot press machine, the low sulfur-content layer existing near the interface was disappeared. It meant that the free sulfur migrated through the resorcinol-resin concentrated layer, which formed by the rubber vulcanizing process, and then reached to the metal surface. It may be suggested that the reaction of sulfur and surface metal brings the degradation of adhesion.
On the other hand, after aging test at 70 C° under RH 95 % for 30 days, the resorcinol-resin concentrated layer existing near the interface was degraded. It was shown that the degradation came mainly from the scission of resinrubber bond, as the results of aging tests of SBR/ Zinc powder /RH model compounds.