Aluminum Anodizing Process Introduction

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1. Degreasing

It is mainly to remove iron sand and oil stains on the surface of the parts to prevent them from affecting the subsequent surface treatment.The main components of the degreasing tank liquid of the project are sodium hydroxide and sodium carbonate, the working temperature is 45-55, the working time is 3-7min, and the pH value: alkaline.The degreasing waste tank liquid L1 is treated as a high-concentration waste liquid in the wastewater station of the plant.

2. Alkaline washing

The function of alkaline washing is to chemically treat the uneven metal surface to give smooth luster. This project uses caustic soda treatment.

The waste tank liquid is replaced regularly, once every two months, and the waste lye L2 is treated as a high-concentration waste liquid in the wastewater station of the plant.

3. Neutralization

That is, the black film is stripped, and the black aluminum salt film formed in the alkaline washing process is removed with dilute nitric acid. Working temperature: room temperature, working time: 20-80 seconds. After neutralization, wash 2 channels with tap water to produce washing wastewater W2.

The waste neutralization tank liquid generated by the neutralization is replaced every three months, and the waste tank liquid S4 is entrusted to a qualified unit for processing.

Neutralization and cleaning produce NOx exhaust gas G2.

4. Chemical polishing

It is a method of chemically treating uneven metal surfaces to give smooth luster. The chemical polishing method of aluminum is to repeatedly immerse the workpiece in a mixed solution such as nitric acid and sulfuric acid to preferentially dissolve the protruding parts until a smooth and shiny surface is formed. The chemical polishing process used in this project requires low light-emitting ability. A certain proportion of phosphoric acid, nitric acid and sulfuric acid is mixed, and the specific gravity and temperature are controlled to increase the polishing time to meet the product gloss requirements. After chemical polishing, wash one with tap water to produce washing wastewater W2-1.

5. Neutralization

Use a certain concentration of nitric acid solution to fine-tune the polishing degree to achieve the desired effect. Working temperature: room temperature, working time: 20-80 seconds. After neutralization, two water washes produce washing wastewater W2.

The waste neutralization tank liquid generated by the neutralization is replaced every three months, and the waste tank liquid S4 is entrusted to a qualified unit for processing.

6. Anodizing

Anodizing is to use metal or alloy parts as anodes, and use electrolysis to form oxide films on the surface. The metal oxide film changes the surface state and performance, such as surface coloring to improve corrosion resistance, enhance wear resistance and hardness, and protect metal surfaces.

7. Neutralization

Before coloring, the oxide film is activated with acid solution to dissolve some of the anodic oxide film material and increase the porosity. Improve the ability to adsorb dyes.

8. Dyeing

The anodized workpiece is immersed in the organic dyeing solution pH value: 5.0-6.5, heated to about 40 degrees Celsius, the heating time is adjusted according to the type of fuel and the required color density, about 3 minutes to 5 minutes Within range. Organic dye ingredients: dye 45.1%, dextrin: 42.7%, sodium acetate: 10.6%, antibacterial agent: 1.5%, silicon defoamer: 0.10%. The color fastness of organic dyes is relatively high.

9. Sealing

Hole sealing is a process in which the porous layer on the outer surface of the oxide film is sealed after the aluminum profile is anodized to reduce the pores of the oxide film and its adsorption capacity. After the aluminum material is anodicized, a porous oxide film composed of a barrier layer and a porous layer is formed on the surface. This layer of oxide film has high surface activity and is susceptible to corrosion and adsorption of dirt. Therefore, the last process of surface treatment of aluminum materials should be sealed. Sealing holes in a metal salt solution not only occurs the hydration reaction of the oxide film, but also there is a process in which the salt hydrolyzes to form hydroxides or the metal ions react with dye molecules to form new metal complexes and precipitate in the membrane pores. , They work together to close the pores. This treatment method is also called precipitation sealing.

After sealing the hole, wash 2 channels with tap water and 1 channel with hot pure water.

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