Brief analysis of the causes of color difference in electrolytic coloring of aluminum profiles

The electrolytic coloring of aluminum profiles has good decorative properties, so it is widely used at home and abroad, especially in the production of surface treatment of architectural aluminum profiles. At present, the main process is to use tin-nickel mixed salt electrolytic coloring, and the color of the products produced is mainly champagne. Compared with the single nickel salt coloring, the tin-nickel mixed salt electrolytic coloring product has brighter color and full color; the main problems It is the color difference of the product, and the unreasonable extrusion process and oxidation coloring process in the production process of aluminum profile will cause the color difference of the product.

The influence of extrusion process on oxidation coloring is mainly the influence of die 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 knead 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 surface of the profile also affect the oxidation coloring. Extrusion temperature, speed, cooling method and cooling time are different, so that the structure of the profile is not uniform, and also produces color difference.

Anodizing 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 colors. The vertical oxidation tank is 7.5m deep, and the upper and lower tank liquids are prone to temperature differences. The temperature is important for anodization. As the temperature is high, the oxidation bath solution will intensify the dissolution of the oxide film, and the pore size on the surface of the porous anodic oxide film will increase. On the contrary, the pore size on the surface of the porous anodic oxide film will be smaller. In addition, the higher the temperature, the higher the porosity of the anodic oxide film, and vice versa. Electrolytic coloring is mainly to make the metal ions of the coloring solution undergo an 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 solution are deposited on the bottom of the anodic oxide film hole to scatter incident light. But showing different colors, the more substances deposited in the micropores, the darker the color. Under the condition of passing the same amount of electricity, the same amount of metal or metal compound is deposited on the high and low temperature parts. For the parts with high porosity and large surface pores, the average deposit per hole is less, so the color is relatively Lighter, on the contrary, the color is darker, resulting in two colors of the coloring material. In the anodic oxidation process, the conductivity has an influence on the oxide film, and it can also cause the color difference of the coloring material. This problem is easy to occur in the horizontal production line, mainly because the oxidized blank is in the upper row process before oxidation Tightness leads to poor conductivity of individual materials, which makes the oxide film relatively different. After coloring, chromatic aberration will occur.

The electrolytic coloring process can directly reflect the color difference problem. The current distribution ability of the electrolytic coloring solution has a decisive influence on the uniform coloring of the coloring material. Once the current distribution is uneven, it will cause obvious color difference. The current distribution ability of the bath is mainly related to the conductivity and polarization of the bath. The coloring liquid contains a certain amount of conductive salt, which is mainly to improve the conductivity of the coloring liquid. When the conductive salt is not supplemented in time, the conductivity will decrease and the current distribution ability will decrease, which will cause chromatic aberration. In addition, the additives in the coloring liquid will produce characteristic adsorption, thereby increasing the degree of polarization. Excessive consumption of this substance will reduce the degree of polarization of the electrolyte, reduce the current distribution ability, and 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 differences.

The above mainly introduces several reasons that affect the color difference of the same tank material. The changes in the process parameters of anodizing and electrolytic coloring will cause the color difference between different tank materials. Therefore, the stability of the oxidation and coloring process should be controlled in the production. , To ensure that the parameters are consistent, thereby reducing the occurrence of the color difference of the oxidized colorant.