| Cold rolled steel has been one of the most useful materials for manufacturing because of its excellent mechanical properties, heat resistance, strong durability and low cost. But the application of cold rolled steel is limited by its poor corrosion resistance, the study for protecting it from corrosion is always an important project.Corrosion inhibitors, cathodic protection and barrier protection are the three major corrosion control methods used in recent years. Barrier protection can separate the metal substrate from corrosive environment. Organic coating is the best method to create such a barrier. Due to the excellent physical and chemical properties, waterborne acrylic coating has been one of the most widely used coatings.A common failure mechanism for organic coatings is degradation due to ultraviolet radiation (UVR) and corrosive environment. When the coatings are exposed in the air, a lot of factors form the corrosive environment and the materials are corroded gradually. Incorporation of pigments and fillers in the coating is a modern approach to overcome these disadvantages.The main inorganic materials for UV absorbers are nano materials, which include nano-TiO2, nano-ZnO, nano-SiO2, nano-Al2O3and so on, because of its non-toxic, tasteless and excellent ultraviolet shielding property, nano-materials has become the focus of UV coating. Besides, the unique physical properties of nano-materials can enhance the density of coating and improve the corrosion resistance of the coating.Although nano-TiO2/ZnO composite coatings have occasionally been reported in the literature, the anti ultraviolet and corrosion behavior of TiO2/ZnO particles based on organic coatings were few studied. So, in this study the nano-composite coatings were formed by dispersing nano-TiO2/ZnO as pigments with different concentrations in pure waterborne acrylic coating. The modified coatings were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV) spectroscopy and electrochemical impedance spectroscopy (EIS). It was found that:(1) When nano-particles are composited in the coating under a reasonable concentration, most of them disperse evenly. When the concentration of nano-ZnO is higher than6wt%, it exhibits heavy agglomeration, which is not suitable to be the pigments or fillers of the coatings.(2) Compared to the unmodified coatings, the modified ones show stronger ultraviolet resistance and the nano-TiO2/ZnO composite particles make up the ultraviolet shielding defects on a particular wavelength by single powder. With incorporation of nano-particles, ultraviolet resistance of the coating increases in the wavelength ranges from280-400nm. When the concentration of nano-TiO2/ZnO is3:5, the ultraviolet resistance of the coating is the best.(3) The corrosion resistance of the coating is improved obviously when it is modified by nano-particles, and the corrosion resistance of nano-TiO2/ZnO composited coatings is stronger than the single ones. With incorporation of nano-particles, corrosion resistance of the coating increases. When the concentration of nano-TiO2/ZnO is3:5, the coating shows the least porosity and the ultraviolet resistance of the coating is the best. |
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