hard anodizing

Anodizing is carried out in the presence of high voltage electricity, it is an electrochemical reaction process; it is a pure chemical reaction.

hard anodizing

The full name of hard anodizing is hard anodizing treatment. The hard anodizing treatment of aluminum alloys is mainly used for engineering or military purposes. It is suitable for both deformed aluminum alloys and die-cast alloy parts. Hard anodized film generally needs a thickness of 25-150um, most hard anodized films have a thickness of 50-80um, and hard anodized films with a film thickness of less than 25um are used for gear keys and spirals. The thickness of the anodic oxide film for parts, wear resistance or insulation is about 50um.

Under certain process conditions, it is necessary to produce a hard anodic oxide film with a thickness of more than 125um, but it is necessary to pay attention to the anodic oxide film. The thicker the oxide film, the lower the microhardness of the outer layer can be, and the roughness of the film surface increases. The bath solution of hard anodized anode is generally sulfuric acid solution and sulfuric acid plus organic acid, such as oxalic acid, sulfamic acid, etc.
 

 
 

Main features of hard anodizing:

1: Color The film is gray, brown, dark green to black, which is related to the material composition and process, and the lower the temperature, the thicker the film, the darker the color.

2: The thickness of the film layer can reach up to 250 microns, so it is also called thick film oxidation.

3: Hardness The hardness of the oxide film is extremely high, HV=1200-1500 on pure aluminum, and the hardness is significantly reduced on alloy aluminum. HV=400-800, because the micropores can absorb lubricant, it can greatly improve the wear resistance.

4: Corrosion It has extremely high corrosion resistance, especially in industrial atmospheres and marine climates.

5: The binding force is very strong with the body.

6: Insulation and thermal insulation hard film resistance is large, the film layer is 100 microns, can withstand more than 2000 volts, the melting point is 2050 degrees Celsius, and the thermal conductivity is as low as 67KW/(M.K), which is an excellent heat-resistant material.

Casting aluminum alloys usually require hard anodizing to improve their properties. Aluminum, silicon-based alloys and aluminum-copper-based alloys are commonly used in cast aluminum alloys. For structural parts and components, copper and magnesium are sometimes added to improve mechanical properties and heat resistance. Aluminum-copper series are also commonly used casting alloys, mainly used for sand castings with large dynamic and static loads and uncomplicated shapes.

The electrolyte and power waveform of cast aluminum alloy need to be improved due to the non-metallic elements. Generally, some metal salts or organic acids, sulfuric acid-oxalic acid-tartaric acid solution, sulfuric acid-oxalic acid-tartaric acid solution, sulfuric acid can be added to the electrolyte. Sulfuric acid-dry oil solution; the power supply form is generally changed to AC and DC superposition, asymmetric current, pulse current, etc., among which the pulse effect is better. Before the electroforming parts are oxidized, the water chestnut should be guided and the burrs should be removed to prevent the current concentration.
 

Application of hard anodizing performance

Due to the high-quality properties of hard anodizing, it is widely used. Mainly used for aluminum parts with high heat resistance, wear resistance and high insulation performance requirements, mainly used in aerospace, marine fleet, petroleum machinery, medical equipment, textile machinery.
 

 The difference between hard anodizing and ordinary anodizing

One, different thickness:

The thickness of hard oxide is thicker than that of ordinary oxide. Generally, the thickness of ordinary oxide film is 8--12UM, and the thickness of hard oxide film is generally 40--70UM.
 

Second, the hardness is unreasonable:

Hardness: ordinary oxidation is generally HV250--350, and hard oxidation is generally HV350--550.
 

Third, the temperature is different:

Generally around 18-22°C, with additives it can reach 30°C. If the temperature is too high, powder or cracks may occur; hard oxidation is generally below 5°C, relatively speaking, the lower the temperature, the higher the hardness.
 

The thickness of hard oxide is thicker than that of ordinary oxide. Generally, the thickness of ordinary oxide film is 8--12UM, and the thickness of hard oxide film is generally 40--70UM. Hardness: ordinary oxidation is generally HV250--350, and hard oxidation is generally HV350--550. Increased insulation, increased wear resistance, increased corrosion resistance, etc. But the price will also increase more.

2022-05-16 14:07:22 | Published by yoyike | Source: Yoyike   Author: @Joe Green

Tag: hard anodizing



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