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Polishing anodized process

Polishing anodized is to electrolyze the conductive acidic electrolyte through current, so as to anodize the aluminum metal surface constituting the anode, and naturally grow a thick and dense alumina protective film on the aluminum surface. This oxide film is not an additional layer and will not peel off. The oxide film is transparent and colorless, and the microcrystalline structure is hexagonal honeycomb. It can not only use the natural color of aluminum to highlight the strong metal feeling, but also color evenly in the micropores to give the curtain wall gorgeous color, which greatly broadens the application field of vision.


The anodized aluminum oxide veneer with standard thickness oxide film (3um) will not change color, corrode, anodize or rust for a long time. The anodized alumina veneer with thickened oxide film (10um) can be used outdoors and can be exposed to the sun for a long time without discoloration.


Tri acid polished anodized color aluminum profile is a necessary aluminum profile for high-grade decoration in interior decoration, hotel lobby, hospital and school. It has strong metal texture, color diversity and color stability.

Brief description of process flow:

(1) Degreasing: because the oil stain adhered to the extruded aluminum profile during processing, storage and transportation will form an oil film on the surface of the substrate, on the one hand, it will affect the adhesion between the surface covering layer and the metal inside the substrate, on the other hand, it will reduce the firmness between the spraying layer and the substrate, so degreasing treatment is required. Sulfuric acid (H2SO4) is used for oil removal, and the general concentration is 100g / L. the specific concentration depends on the material and quality requirements of aluminum profile. The tank liquid is not replaced and only needs to be replenished continuously at ordinary times. As the degreasing process is carried out at room temperature and acid mist inhibitor is added, a certain amount of acid mist is generated in this process. This process produces replaced waste acid.

(2) Three pass cleaning: after oil removal, the water washing is carried out in the water washing tank. There are 3 water washing tanks in total, and the countercurrent water washing method is adopted. Therefore, acid cleaning wastewater is produced in this process.

(3) Alkali corrosion and secondary cleaning: remove the oxide film on the surface of aluminum profile through the corrosion of strong alkali. The alkali corrosion process is exothermic reaction, so the anti-corrosion coil is configured in the alkali corrosion tank, and the chilled water jacket is used to cool the alkali corrosion liquid. 40g / L sodium hydroxide solution is used for alkali corrosion. Alkali mist will be generated during alkali corrosion and will enter the alkali mist absorption tower for absorption and purification treatment. After alkali corrosion, it needs to be cleaned with water, two-step cleaning and countercurrent water washing to remove the residual alkali solution on the surface and produce alkaline cleaning wastewater.

(4) Neutralization and one-step cleaning: ash hanging on the substrate surface after alkali corrosion, so 50g / L sulfuric acid solution is required for acid pickling neutralization. The purpose of neutralization is to adjust the pH value of the substrate surface. Since the neutralization process is carried out at room temperature, the sulfuric acid concentration is low, and acid mist inhibitor is added, a small amount of acid mist is generated in this process; After neutralization, it needs to be washed with tap water, and the leaching method is adopted to remove the residual acid on the surface to produce acid washing wastewater.

(5) Oxidation and secondary cleaning: a dense aluminum oxide film is formed on the surface of aluminum to prevent corrosion. The anodizing electrolyte is 150g / L sulfuric acid. The oxidation principle is to produce oxygen and hydrogen through water electrolysis. The primary oxygen reacts on the surface of aluminum profile to form aluminum oxide film. At the same time, when hydrogen overflows, sulfuric acid will be brought out to form acid mist and enter the acid mist absorption tower for purification treatment.

The temperature of the oxidation tank liquid will rise under the action of direct current. In order to control a certain temperature of the oxidation tank (the process requires that the liquid temperature be maintained at about 20 ℃), an anti-corrosion coil is set in the oxidation tank and a water jacket is used to cool the oxidation tank liquid.

After oxidation, tap water shall be used for washing. The cleaning principle is the same as the “two-step water washing” after alkali corrosion to remove the residual acid on the surface and produce acidic cleaning wastewater.

Polish anodized coloring of aluminum profile

(6) Dyeing and countercurrent cleaning: according to the customer’s requirements, the aluminum profile needs to be dyed after oxidation. According to different colors, six dyeing tanks are set in the project. The dyeing is carried out by immersion dyeing at room temperature. It is soaked in the dyeing tank for 1 ~ 3 minutes according to the color depth, and then taken out to dry. The dyes of the project are mainly composed of metal complex dyes, dextrin, sodium acetate, etc. according to the SGS test report of the dye, no heavy metals such as lead, mercury, cadmium and hexavalent chromium have been detected in the dye. After dyeing, pure water shall be used for countercurrent cleaning. The countercurrent cleaning process produces cleaning wastewater.

(7) Normal temperature sealing, medium temperature sealing and two-step cleaning: the purpose of sealing is to change the crystal arrangement of alumina membrane and make the crystal arrangement structure of alumina membrane compact. In this project, normal temperature sealing and medium temperature sealing shall be carried out according to the dyeing depth of profile, normal temperature sealing shall be carried out for light color and medium temperature sealing shall be carried out for dark color. Nickel acetate is used as the pore sealing agent. When the pH value is about 5.8, nickel acetate is hydrolyzed to form nickel hydroxide, which is adsorbed at the opening of the micropore, which can effectively achieve the purpose of pore sealing. Medium temperature sealing hole adopts electric heating. There are two sealing grooves: normal temperature sealing groove and medium temperature sealing groove. The groove liquid does not need to be replaced, but only needs to be continuously supplemented at ordinary times.

After the medium temperature sealing, the hole shall be cleaned twice with hot water to remove the residual nickel acetate on the surface. Hot water cleaning adopts electric heating to control the water temperature. This process produces cleaning wastewater.

(8) Drying: remove the moisture on the surface of the sealing parts, and use electric heating for drying.

Post time: Nov-05-2021