Research On The Weather Resistance And Preparation Of Water-based Chromium-free Zinc Aluminum Alloy Coating

Dacromet coating is also called "Zinc Aluminum chromium coating", is a kind of coating with high anti-corrosion performance. Compared with the traditional coating process, such as electric galvanized, electroplating chromium, its safety loop coating process preparation of the coating on the "green production". But the chromium of dacromet coating is a serious carcinogenic substances and heavy metal pollutants, which leads the limitation of the coating.The article takes the flake zinc-aluminum alloy powder instead of the mixed powder to prepare the coating, in order to improve the uniformity and improve the corrosion resistance of the coating. It also studies the coating corrosion resistance and the weather resistance in a complicated environment, which is the key point of the research. The main purpose of the research is to gain a kind of coating with excellent corrosion resistance, and can be served under the condition of complex climate for a long time.First, the article designs the L16(45) orthogonal experiment, which takes four kinds of Zinc alloy powder(20% Al- Zn- 1.6% Si, Al- 30% Zinc- 1.6% Si, Al- 40% Zinc- 1.6% Si, Al- 55% Zinc- 1.6% Si), four dispersants and the content of the two as the main factors. And the adhesion strength of the coating, exterior morphology and corrosion resistance has been evaluated. The experiments an its results leads to the optimal formula of the coating.Second, the article thoroughly does the research the corrosion resistance ability. Comparative studies on the salt-water resistance of the coatings made by 20 %Al-Zn-1.6 %Si, 30 %Al-Zn-1.6 %Si, 40 %Al-Zn-1.6 %Si, 55 %Al-Zn-1.6 %Si alloy powder have been done. The optimized coating liquid viscosity, degree of fineness, p H are analyzed, so does the thickness of the coating and surface morphology. The salt water resistance, salt spray test and electrochemical corrosion resistance performance is evaluated, the corrosion resistance mechanism is analyzed.The weather resistance of the coating is the key point of this paper. The optimized coating has been made, and tests have been done on the typical environment, the weathering mechanism and the law of the weather resistance is analyzed.The research uses XRD, SEM, EDS and other methods to analyze the coating, the properties of each test are discussed and analyzed in this paper, especially the mechanism.