Abstract: A combined molybdate-tannic acid passivation treatment on galvanised steel is studied in this paper.Copper decoration drop tests indicated that the combined molybdate-tannic acid passivated samples showed better corrosion resistance than that of samples treated separately by molybdate or tannic acid.The electrochemical behaviours of the passivated samples were investigated using potentiodynamic polarisation and electrochemical impendence spectra in 0.5 mol/L^-1 NaCl solution and showed corrosion current densities of 4.95×10^-5,9.80×10^-5and 1.47×10^-4A.cm^-2 respectively.Electrochemical impendence spectra also indicated that molybdate-tannic passivated samples exhibited worse corrosion resistance than that of molybdate passivated samples.The mechanism of molybdate-tannic acid passivation on galvanised steel is discussed in brief.