At present, the application of single-color anodized aluminum alloy building profiles in practice has been significantly reduced, and electrolytic coloring oxide films, organic coloring oxide films, porcelain oxide films, hard oxide films, and imitation stainless steel oxide films based on them have been significantly reduced. Has been widely used. For the oxide film coloring technology, the factors affecting aluminum oxide coloring are:
1. Factors affecting the coloring quality of oxide film
(1) Regardless of anodic oxidation film formation or electrolytic coloring, surfactant-based additives and stabilizers must be added. The purpose is to stabilize the film formation speed and film thickness, inhibit the dissolution of the oxide film and improve the coloration. Uniformity.
(2) Time: The coloring time will also affect the coloring quality and color resistance. For example, the coloring time is short, the color is easy to fade, the time is long, the color is too dark, and the surface is easy to bloom.
(3) The coloring temperature has a great influence on the coloring. When the temperature is lower than 15 ° C, the coloring speed is slow. If the temperature is too high, the coloring film will fog, and the Sn salt will easily hydrolyze the antigen, causing the tank liquid to become cloudy.
(4) When the concentration of Sn salt in the electrolytic solution is too low, the coloring speed is slow, and when the concentration is higher than 25g / L, the coloring speed is fast, but it is not easy to grasp, and the color difference is often large.
(5) When the coloring voltage is low, the coloring speed is slow, the color change is slow, and uneven color tone is easy to occur. When the voltage is high, the coloring speed is fast and the coloring film is easy to peel off.
In addition, the pH value, water quality, and coloring tank materials all have a certain effect on the coloring quality. Only by ensuring that each parameter is within the control range can the quality of the electrolytically colored oxide film be guaranteed.
2. Influence of impurities in electrolytic solution The degree of coloration of aluminum alloy products depends largely on the quality of oxide film formation. Therefore, in the sulfuric acid anodizing solution, the influence of impurities on the oxide film cannot be ignored. The impurities are mainly metal ions such as copper, iron, aluminum and organic pollutants. They must be removed in time to maintain the normal range of use of the solution.
(1) Copper ions will be replaced and deposited on the surface of aluminum parts, causing loose pores of the oxide film, and reducing transparency, corrosion resistance and electrical insulation performance. Therefore, the copper ion content is not allowed to exceed 0.02g / L.
(2) Chloride ions come from tap water or cooling water after the cooling pipe is ruptured. The content of chloride ions should be less than 0.2g / L, otherwise the resulting oxide film is rough and loose. In severe cases, the surface of aluminum parts will be corroded (break down).
(3) The aluminum ions in the aluminum ion electrolyte gradually increase. When the content is greater than 25g / L, the conductivity of the electrolyte decreases, and the surface of the product appears white spots or massive white spots, which reduces the adsorption capacity of the film layer and makes dyeing difficult. .
(4) The iron ion in the iron ion electrolyte must not exceed 0.2g / L, otherwise dark streaks will appear.