It is well known that the corrosion resistance of galvanized steel can be greatly improved by means of suitable chromate based passivation.The effectiveness of chromate based passivation is without question although there are many problems with regard to their environmental suitability.Accordingly,it is of outstanding importance to develop environmentally friendly passivation treatment with good protective effectiveness against corrosion.In this work,in order to find applicable alternatives to chromate passivation,a novel cationic polyurethane dispersion ( CPUD ) with excellent tolerance against electrolytes was firstly synthesized.Furthermore,a novel chrome-free passivation hybrid was prepared by mixing the synthesized CPUD with non-chromate passivation agent.The structure of CPUD was confirmed by fourier transfer infrared ( FTIR) and dynamic light scattering ( DLS).In particular the stability against electrolytes and compatibility with passvation agent of CPUD were evaluated,respectively.The properties of chromate conversion coating on the surface of galvanized steel were also investigated.The new hybrid provides a potential non-chromate alternative to the traditional chromated passication treatment.