The electrolytic coloring of aluminum profiles has good decorative properties, so it is widely used at home and abroad, especially in the surface treatment production of architectural aluminum profiles. At present, the main process is to use tin-nickel mixed salt electrolytic coloring, and the color of the product produced is mainly champagne. Compared with single nickel salt coloring, the color of the product produced by tin-nickel mixed salt electrolytic coloring is bright and full; the main problem is that the product has color difference. The unreasonable extrusion process and oxidation coloring process in the production process of aluminum profiles will lead to color difference in the product.
The influence of extrusion process on oxidation coloring is mainly the influence of mold design, extrusion temperature, extrusion speed, cooling method, etc. on the surface state and uniformity of the extruded profile. The mold design should be able to fully blend the feed, otherwise it is easy to have bright (dark) band defects, and color separation may appear on the same profile; at the same time, the mold state and the extrusion lines on the profile surface also affect oxidation coloring. Different extrusion temperatures, speeds, cooling methods and cooling times make the profile structure uneven, which will also produce color differences.
Anodic oxidation has a very important influence on the color difference of electrolytic coloring, especially in the production process of vertical oxidation line, it is easy to have two-end color. The vertical oxidation tank is 7.5m deep, and the upper and lower tank liquids are prone to temperature differences. Temperature has an important influence on anodization. When the temperature is high, the dissolution of the oxide film by the oxidation tank liquid intensifies, and the pore size on the surface of the porous anodized film will increase. On the contrary, the pore size on the surface of the porous anodized film is smaller. In addition, when the temperature is high, the porosity of the anodized film is higher, and on the contrary, it is lower. Electrolytic coloring mainly makes the metal ions of the coloring liquid undergo electrochemical reduction reaction on the surface of the barrier layer in the micropores of the oxide film, so that the metal ions in the coloring liquid are deposited at the bottom of the anodized film holes, scattering the incident light and showing different colors. The more substances deposited in the micropores, the darker the color.
The electrolytic coloring process can directly reflect the color difference problem. The current distribution capacity of the electrolytic coloring liquid has a decisive influence on the uniform coloring of the coloring material. Once the current is unevenly distributed, it will cause obvious color difference. The current distribution capacity of the bath liquid is mainly related to the conductivity and polarization of the bath liquid. The coloring liquid contains a certain amount of conductive salt, mainly to improve the conductivity of the coloring liquid. When the conductive salt is not added in time, the conductivity decreases, the current distribution capacity decreases, and color difference will occur. In addition, the additives in the coloring liquid will produce characteristic adsorption, thereby increasing the polarization. Excessive consumption of this substance will reduce the polarization of the electrolyte, reduce the current distribution capacity, and also cause color difference. In actual production, it is necessary not only to improve the conductivity of the bath liquid, but also to ensure that the conductive rod and the copper seat have good conductivity. Poor conductivity will cause uneven distribution of power lines and produce color difference.
