Electrolytic coloring of aluminum profile has good decoration, so it is widely used at home and abroad, especially in the surface treatment production of architectural aluminum profile. At present, the main process is electrolytic coloring with tin nickel mixed salt, and the color of the product is mainly champagne. Compared with single nickel salt coloring, the color of electrolytic coloring with tin nickel mixed salt 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 of aluminum profile will lead to color difference.

The influence of extrusion process on oxidation coloring is mainly the influence of die design, extrusion temperature, extrusion speed and cooling mode on the surface state and microstructure uniformity of extruded profiles. The mold design shall be able to make the feed fully knead, otherwise it is easy to have bright (dark) band defects, and color separation may occur on the same profile; At the same time, the die state and the extrusion lines on the profile surface also affect the oxidation coloring. Different extrusion temperature, speed, cooling mode and cooling time will lead to uneven structure and color difference.

Anodizing has a very important impact 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, the temperature difference between the upper and lower tank liquid is easy to occur, and the temperature has an important impact on anodizing. When the temperature is high, the oxidation tank liquid intensifies the dissolution of the oxide film, and the pore diameter of the porous anodic oxide film surface will increase. On the contrary, the pore diameter of the porous anodic oxide film surface is small. In addition, the porosity of anodic oxide film is higher when the temperature is high, and vice versa. Electrolytic coloring is mainly to make the metal ions in the coloring solution carry out 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 at the bottom of the anodic oxide film hole, scattering the incident light and showing different colors. The more substances deposited in the micropores, the darker the color. Under the condition of passing the same electric quantity, the same amount of metal or metal compound is deposited on the parts with high and low temperature. For the parts with high porosity and large surface pore diameter, the average sediment of each hole is less, so its color is relatively light, on the contrary, its color is darker, resulting in the two ends of the coloring material. In the process of anodizing, the conductivity has an impact on the oxide film and will also cause the color difference of the coloring material. This problem is mainly easy to occur in the horizontal production line. It is mainly because the clamping material is not tight during the upper row of the oxidized blank before oxidation, resulting in the poor conductivity of individual materials, which makes the oxide film relatively different. After coloring, the color difference will occur.

Electrolytic coloring process can directly reflect the color difference. The current distribution ability of electrolytic coloring solution has a decisive impact on the uniform coloring of pigment. Once the current distribution is uneven, it will cause obvious color difference. The current distribution capacity of the tank liquid is mainly related to the conductivity and polarity of the tank liquid. The coloring solution contains certain conductive salt, which is mainly to improve the conductivity of the coloring solution. When the conductive salt is not added in time, the conductivity and current distribution capacity will be reduced, which will cause color difference. In addition, the additive in the coloring solution will produce characteristic adsorption, so as to increase the polarization. Excessive consumption of this material will reduce the polarization of the electrolyte, reduce the current distribution capacity, 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 copper base have good conductivity. Poor conductivity will cause uneven distribution of power lines and color difference.