A pretreatment solution and process for pretreating steel substrates with an aqueous solution to form a thin partially crosslinked layer that passivates the steel surface and inhibits the formation of flash rust, in which the thin partially crosslinked layer is dried in ambient air, and the dried layer enhances the cathodic disbondment resistance of the overlying paint system. In the process an aqueous precursor solution (A) containing at least one amino-functional silane, at least one of a dissolved silicate or a dissolved aluminate and at least a metal salt; is mixed with an aqueous precursor solution (B) containing at least an epoxy resin. The molar amount of amino-functional silane in precursor solution (A) is at considerably lower than the stoichiometric amount that is needed for completing the crosslinking reaction with the epoxy resin in precursor solution (B) so that unreacted epoxy groups are made available for further crosslinking with the overlying paint.