The invention is directed to an acidic aqueous metal pretreatment solution that comprises amino-functional organosilanes, complex anions of the elements Zr, Ti, Hf and/or Si as well as oxyacids of phosphorus; a process for the treatment of metal substrates, especially selected from zinc and zinc-coated steel substrates, wherein metal pretreatment solutions of this invention are applied to reduce corrosion when applied to metal surfaces and in addition confer good adhesion properties for subsequently coated organic lacquers.