Based on the chromium - free passivation technology for the galvanized layer, the advantages and disadvantages of four composite passivation systems with silane, tannic acid and phytic acid used as the main film - forming substances were summarized, from the aspects of the properties of the passivation film, the stability of the passivation solution and the corrosion resistance mechanism of the film. Results showed that the silane system had the best corrosion resistance and stability. Tannic acid and phytic acid systems could obtain rich colors through different compounding methods, but the surface conditions were poor. The corrosion resistance mechanisms of tannic acid and phytic acid were similar. The environment of the passivation solution caused tannic acid or phytic acid to react with Zn2+ to form a complex and form a chelate ring to attach to the surface of the substrate, while the silane could combine with organic corrosion inhibitors and inorganic complexes respectively to form the Si - O - M covalent bond. The best compatibility principles of each system were listed. This comparative study showed that the silane system had a better application prospect in being used as the main film - forming substance. Its film had excellent corrosion resistance, the most stable structure with the least defects. It could have a synergistic corrosion inhibition effect with various types of corrosion inhibitors, making the film have good corrosion resistance and self - repairability.
