| Metal material is an essential part of industrial and life now, and stainless steel is the one of the most wide-used material. However, due to the existence of corrosion problems, the use of the scope and age has been greatly restricted, and it causes serious economic losses to the national economy. The problems of corrosion and protection in stainless steel materials have long been concerned. The formation or application of protective coatings on metal surfaces is the most important and common method to prevent or control metal corrosion. There are many methods to prepare the coating, such as hydrothermal method, sol-gel method, and physical vapor deposition method. As above, sol-gel method has the advantages over others because it needs lower synthesis temperature and is easy to control reaction condition, and the equipment and technological is much simple. The coatings obtained is of high purity and excellent uniformity as well. What’s more, it can obtain desired thickness and grouped thin film, which has the potential of industrial application, thus receives widespread attention.The present study adopted sol-gel method, in which organic tetrabutyl titanate was used as the precursors of titanium dioxide, ethyl silicate as the precursor of silica, aluminum nitrate and zinc acetate as raw materials for reaction of alumina and zinc oxide, ethanol as the solvent and acetic acid as catalyst, thus SiO2-TiO2-Al2O3-ZnO multiple sol-gel composite coatings were prepared on stainless steel. In the preparation of coating process by dip coating method, the coating sol were spread over stainless steel surface that was deposed, After certain temperature sintering, the whole process made the coating coated on the surface of stainless steel compactly and smoothly. At last, the structure and corrosion resistance of the coating were analyzed by differential thermal analyzer（TG-DTA）, X ray diffraction, scanning electron microscopy（SEM）, electrochemical workstation and so on.From the change of viscosity with time, we could see that in the process of Precursors hydrolysis reaction, when n（H2O）/n（TiO2+SiO2+Al2O3+ZnO）=4, the overall sol system was the most stable, and the most suitable for coating. Based on TG-DTA thermal analysis of coating, the optimum sintering temperature of the coating was about 500℃. According to analysis of XRD under different heat treatment temperature showed that when the sintering temperature was above 500 ℃, grain inside the coating was refined and correspondent oxide crystals were generated. In addition, the higher temperature was, the higher degree of grain refinement would be. After SEM analysis of coating with the same component of different heat treatment temperatures and the different components of the same heat treatment temperature was corroded before and after in Na Cl, we noted that when the heat treatment temperature was 500 ℃, SiO2:TiO2:Al2O3:ZnO=4:4:1:1, the composite coating prepared was dense and has a smooth surface as well as the best corrosion resistance. |
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