Abstract: A method is disclosed for improving the hydrolytic stability of the adhesive bond between an RFL type organic adhesive and a steel reinforcing element in steel-rubber composite articles. This is achieved by a pre-treatment of the steel surface before it is coated with the organic adhesive. The pre-treatment includes first immersing the steel element in an aqueous bath containing an acid, or base followed by a water rinse. A primer coating is then applied onto the surface of the steel element which consists of an organo-silane compound of the following formula:X -- R.sup.1 -- Si -- (OR.sup.2).sub.3where X is an amino, glycidoxy or an aminoethyl radical; and wherein R.sup.1 is an alkylene radical of from 2 to 4 carbon atoms when X is amino or glycidoxy and --HN--R.sup.3 --, where R.sup.3 is an alkylene radical of from 2 to 3 carbon atoms when X is aminoethyl; and wherein R.sup.2 is an alkyl of from 1 to 2 carbon atoms.

Abstract: A method is disclosed for improving the hydrolytic stability of the adhesive bond between an RFL type organic adhesive and the steel reinforcing element in steel-rubber composite articles. This is accomplished by a pre-treatment of the steel surface before it is coated with the organic adhesive. The pre-treatment is conducted in a continuous operation which includes the sequential steps of: (1) cleaning the metal surface by a vapor degreasing method or by immersion in a detergent containing aqueous bath followed by a hot water rinse; (2) coating the surface with a crystalline or microcrystalline zinc phosphate; (3) rinsing the phosphated steel surface with water; (4) subjecting the phosphated surface to a chromate or chromic acid rinse; (5) rinsing again with deionized water; and finally (6) drying the steel reinforcing element.