The adhesion property between rubber compounds containing different types of adhesion promoters (resinous adhesion promoter (containing both methylene donor and methylene acceptor), cobalt salt and zinc borate) and different loading amounts of sulfur and brass-plated steel cords was investigated to understand the effect of sulfur loading in the rubber compounds on their adhesion characteristics to the brass-plated steel cords. The adhesion property of the rubber compounds to brass-plated steel cords was largely dependent on both the type of adhesion promoter and the loading amount of sulfur in the rubber compounds. The pull-out force of adhesion samples increased significantly with increasing loading amount of sulfur in the rubber compounds containing resinous adhesion promoter, whereas it decreased slightly with increasing loading amount of sulfur in rubber compounds containing cobalt salt or zinc borate. In humidity aging, the best adhesion retention was observed in the rubber compound containing zinc borate and low loading of sulfur. Regardless of the type of adhesion promoter, adhesion retention after thermal aging treatments improved with increasing loading amount of sulfur in the rubber compounds. The adhesion property was interpreted in terms of the interphases formed between the rubber compounds and the brass-plated steel cords as studied using Auger electron spectroscopy. (c) Koninklijke Brill NV, Leiden, 2008