a metal - coupling composition composed of silane cross - linking and coupling agents wherein the coupling agent includes a vinyl moiety . the coupling composition is a replacement for iron - phosphatizing / chromate primering and chromate primering in zinc phosphatizing processes . in a preferred embodiment , the silane cross - linking agent has the following formula : and x is a trivalent group , each y is independently a divalent group or series of divalent groups , each q is independently — r or — or and each r is independently a c 1 - 10 alkyl group or aryl group , and — or group are hydrolysable ; and the silane coupling agent has the following formula : each q is independently — r or — or and each r is independently a c 1 - 10 alkyl group or aryl group , and — or group are hydrolysable ;