Use of zinc alloy coatings on steel cord reinforcement in vehicle tyres

Tyres which are radically reinforced with high tensile steel cords need to develop a bond between the rubber and the steel. Brass coatings on the cord are currently used to promote the bond but deterioration takes place with time and corrosion of the underlying steel occurs eventually. Zinc-cobalt c oatings have been used as a replacement for brass. These coatings are capab le of being drawn in the cord making operation provided that the cobalt con tent is <1.5%. Pull-out tests after vulcanising show that zinc-cobalt promo tes similar adhesive strengths to that achieved with brass coatings. After ageing in warm moist conditions for up to 16 days the zinc-cobalt coating m aintained higher levels of adhesion than brass. In tyre tests the zinc-coba lt coatings were superior in preventing red rust formation on the steel.