Zn-Al alloy coatings reinforced by SiO_2, TiO_2,ZnO, Al_2 O_3 or TiC nanoparticle were prepared by adding hard nanoparticles to the coating solution to increase the hardness of water-based chrome-free coating, respectively. Microhardness testing and Tafel plots were used to study the influence of the type and content of nanoparticles on the microhardness and corrosion resistance of the coating. The electrochemical corrosion behavior of the optimized coating in 3.5%NaCl solution was studied by electrochemica...