Why does aluminium product processing aluminium alloy need sandblasting oxidation tre
aluhm > 02-25-2018, 06:16 AM
Why does aluminium product processing aluminium alloy need sandblasting oxidation treatment? Why does aluminum alloy need surface oxidation treatment? The surface oxidation of aluminum and aluminum alloy is the most important surface treatment process. The aluminum alloy surface oxidation problem handling q&a based on the current shenzhen aluminum processing plant production needs, combined with the pearl river delta region of aluminium alloy sandblasting oxidation process for decades of production experience, in the form of q&a, blank piece of aluminum oxide before receiving and inspection, oxidation, mechanical finishing, chemical polishing and erosion of electrochemical polishing, oxidation protection before, workpiece clamping, anodic oxidation, anodic oxidation film dyeing and coloring, chemical conversion, and the anode oxidation membrane technology such as closed.
Aluminium and aluminium alloy in the atmosphere can naturally formed a layer of oxide film, but the thin membrane (40-50 a) and porous, for amorphous, inhomogeneous and discontinuous film layer, not as a decorative reliable protective film layer. With the continuous development of aluminum products processing industry, more and more widely in the industry with the method of anodic oxidation and chemical oxidation, in aluminium and aluminium alloy surface generates a layer of oxide film, to achieve the purpose of protection a decoration. The oxide film obtained by chemical oxidation was generally 0.3 ~ 4um, and the properties of soft, abrasion and corrosion were lower than that of anodic oxide film. Therefore, it is seldom used alone except for special purpose. However, it has better adsorption capacity, and it can be applied to improve the corrosion resistance and decoration of aluminum products. The oxide film obtained by anodic oxidation process is generally 5-20v m, and the thickness of hard anodic oxide film can reach 60-2500m. The film layer also has the similar characteristics:
(I) high hardness of aluminum processing. The hardness of pure aluminum oxide film is higher than that of aluminum oxide film. In general, its hardness is related to the aluminum alloy composition and electrolyte process conditions. The anodic oxide film is not only of high hardness but also good wear resistance. In particular, the porous oxide film has the ability to absorb lubricant, and can further improve the abrasion resistance of the surface.
(2) high corrosion resistance of aluminum processing. This is due to the high chemical stability of the anodic oxidation film. The anodic oxidation film of pure aluminum is better than that of aluminum alloy. This is due to the fact that the composition of the alloy or the formation of a metal compound cannot be oxidized or dissolved, which makes the oxide film discontinuous or void, thus greatly reducing the corrosion resistance of the oxide film. Therefore, it is necessary to seal the film after anodic oxidation to improve its corrosion resistance.
(3) aluminum processing has strong adsorption capacity. Anodic oxidation of aluminium and aluminium alloy membrane is porous structure, has a strong adsorption capacity, so give hole filling all kinds of pigments, such as lubricants, resin can be further improve protection, insulation, wear resistance of aluminum products and decorative performance.
(4) aluminum processing has good insulation performance. The anodic oxide film of aluminum and aluminum alloy has no conductive properties of metal and becomes a good insulating material.
(5) strong thermal insulation resistance. This is because the coefficient of thermal conductivity of anodic oxide film is much lower than the pure aluminium anodic oxide film can heat resistance around 15001 c, but pure aluminium can only 660 ℃. In summary, aluminum and aluminum alloys are chemically oxidized, especially after anodic oxidation, and the oxide film formed on its surface has good protective properties. Therefore, it is widely used in aviation, electrical, electronic, mechanical manufacturing and light industry.
Ornamental oxidation
There are many kinds of aluminum and aluminum alloy decorative oxidation process, which can be divided into two categories: chemical oxidation and electrochemical oxidation. Among them, anodic oxidation treatment is widely used. This is because the oxidation film obtained by anodic oxidation is better than that obtained by all chemical oxidation methods.
After chemical or electrochemical polishing of aluminum and aluminum alloy parts, after anodic oxidation treatment, can get bright and clean, high brightness, transparency of oxide film layer, then through dyeing, thunder-and-lightning colour can be obtained by surface. If it is oxidized under a certain technological condition, it can form an imitation glaze layer on its surface, thus obtaining special decorative effect on the surface of aluminum products.
According to incomplete statistics, the decorative oxidation process of aluminum and aluminum alloy in our country has developed to dozens of kinds, making the development of China's aluminum processing industry change with each passing day.
1. Chemical oxidation.
Aluminium and aluminium alloy chemical oxidation treatment, according to the nature of the solution, can be divided into two categories, alkaline and acidic solution oxidation treatment, according to its membrane layer can be divided into the properties of oxide film, chromate, phosphate coatings film and chromic acid ~ phosphate film, etc.
(I) process specification.
1. Specification for chemical oxidation of lye.
Anhydrous sodium carbonate (Na2C03) 50g/L.
Sodium chromate (Na2Cr04) 15g/L.
Sodium hydroxide (NaOH) 25g/L.
Temperature of 80-100 'c
Time 10-20 min
After oxidizing, the parts should be cleaned immediately, and in the 20g/L chromic acid solution and at room temperature for 5 ~ 15 seconds, then clean and dry. The color is golden. The film thickness is 0.5 ~ 1um, suitable for pure aluminum, aluminum magnesium, aluminum manganese alloy.
2. A specification for the oxidation process of phosphate monochromate.
Formula 1: phosphate (H3P04) 50--60mL/L.
Chromic anhydride (Cr03) 20- 25g/L.
Ammonium fluoride (NHOHF2) 3 ~ 3.5g/L.
Boric acid (H3B03) 1 ~ 1.2g/L.
The temperature of 30-36 'C
3 ~ 6 minutes
This method USES phosphoric acid more, so also called phosphating method. The oxide film is colorless to light blue, and the film thickness is about 3-49m. The film layer is dense, the corrosion resistance is high, and the size of the part is unchanged after oxidation, which is suitable for all kinds of aluminum and its alloy. In order to further improve the corrosion resistance, it can also be filled in. Recruit parts by the oxidation after cleaning in the 40-45 g/L of potassium dichromate solution, the temperature is 90-98 ℃, soak for 10 minutes, and then after cleaning in the < = 70 ℃ oven dry can. Suitable for general parts. Can also be in 20 to 30 g/L of boric acid in the solution, the temperature is 90-98 ℃, dipping 10-15 minutes, and then by the cleaning within 70 ℃ oven drying. Suitable for aluminum rivet, etc.
Formula 2: phosphoric acid (H3P04) 45g/L.
Chromic acid drunk (Cr03) 6g/L.
Sodium fluoride (NaF) 3g/L.
Temperature 15 ~ 35 ℃
10-15 min time
Thin film, good toughness, high corrosion resistance, suitable for aluminum and aluminum alloy parts after oxidation.
Formula 3: phosphoric acid (H3P04) 22g/L.
Chromic acid drunk (Or03) 2.--4g/L.
Sodium fluoride (NaF) 5g/L.
Qing acid (H3BOO 2 g/L
At room temperature
15-60 s
This method is also known as chemical conductive oxidation. Oxide film colorless transparent; The film is thin, with a magic of 0.3-0.5 um and good conductivity. It is mainly used for flexible aluminum parts.
3. Formula 1: chromic anhydride (Cr03) 4N 6g/L.
Sodium fluoride (na-f) lg/L.
Potassium ferricyanide [K3Fe (CN) 6] 0.5g/L.
Temperature of 30-35 0 c
20-60 s
The color of oxide film is iridescent, thin film, good conductive performance, mainly used for aluminum electric parts which have certain requirements for conductive performance.
Formula 2: chromic acid drunk (Cr03) 3.5 ~ 6g/L.
Sodium dichromate (NaZCrZO7) 3 ~ 3. 5 g/L
Sodium fluoride (NaF) 0.8g/L.