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Anodizing process of titanium and its alloys

  • Categories:Industry news
  • Author:JWMSC
  • Origin:
  • Time of issue:2021-08-19 14:16
  • Views:0

Summary:

Anodizing process of titanium and its alloys

Summary:

  • Categories:Industry news
  • Author:JWMSC
  • Origin:
  • Time of issue:2021-08-19 14:16
  • Views:0

Anodic oxidation process is a traditional technology of electrolytic oxidation on the surface of metals and their alloys to form oxide films. The oxide films made by this technology have uniform color, corrosion resistance, strong adhesion and good biocompatibility, which have been widely used in modern biomedical field and aerospace field.

The anodic oxidation process of titanium is to use titanium as anode, stainless steel and other metals as cathode, with the help of certain electrolyte, promote the oxidation reaction on the surface of titanium alloy through electrochemical reaction to form oxide film. This layer of oxide film has obvious reflection and refraction effect on light, and oxide films with different thickness will show different colors and have protection at the same time. Therefore, it is an ideal decorative layer and wear-resistant layer, which is widely used in construction, aviation, medicine and other fields.

Anodizing coloring method of titanium and its alloys

The anodizing and coloring process flow of titanium and its alloys is as follows:

Degreasing (strong alkali degreasing agent) → water washing → primary pickling (hydrofluoric acid aqueous solution) → water washing → secondary pickling (hydrofluoric acid + hydrogen peroxide aqueous solution) → water washing → anodic oxidation (constant voltage electrolysis in phosphoric acid aqueous solution) → water washing → sealing → drying.

1. Degreasing

Degreasing is to remove the oil agent remaining on the titanium surface during rolling. Because the water permeability of the attached part of the oil is very poor, uneven coloring is easy to occur when pickling the titanium surface.

2. Initial pickling

The primary pickling is to form pear skin pattern on the surface of titanium and its alloy. Using 5% by weight hydrofluoric acid to wash titanium acid can promote the formation of pear skin pattern.

3. Secondary pickling

Secondary pickling is to remove the powdery dirt formed on the surface by primary pickling. In addition, in order to avoid uneven pickling, it is necessary to use hydrofluoric acid and hydrogen peroxide aqueous solution to make titanium ions become a titanium containing complex to achieve stability after hydrofluoric acid dissolves the surface dirt at one time.

4. Anodizing

Phosphoric acid with 1% weight concentration of electrolyte is used, aluminum plate is used as cathode, and titanium plate after pretreatment is used as anode for constant voltage treatment. With the increase of voltage, the oxide film on the surface of titanium thickens, showing various color changes.

Table: relationship between anodizing voltage, color and film thickness

5. Closed

In order to improve the corrosion resistance, pollution resistance and wear resistance of anodic oxide film, titanium and its alloys need to be sealed with hot water, steam and solutions containing inorganic salts and organic substances after anodizing and coloring.

6. Dryness

After sealing, wipe the moisture on the workpiece with a clean cotton cloth to dry it naturally.

In conclusion, it can be seen that the anodizing process of titanium and its alloys is relatively simple, and the color formed on the surface is rich. In addition, the cost is relatively low, so it is easy to be popularized in industry. It is an oxidation coloring technology with good development prospects.

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