Black Oxidation Treatment Of CNC Machined Parts
The black oxidation treatment of CNC machined parts is a commonly used surface treatment method, mainly used to improve the appearance of metal parts, enhance corrosion resistance and wear resistance. The following is a detailed explanation of CNC Machined Parts black oxidation treatment, including treatment steps, principles, types, and applications:
1、 Processing steps
Cleaning and preparation:
Use alkaline solution to degrease and clean CNC Machined Parts, removing surface oil and dirt.
Rinse off any remaining alkaline solution with distilled water to ensure the surface of the parts is clean.
Rust removal/pickling (if necessary):
If there are rust or oxide stains on the surface of CNC Machined Parts, they need to be soaked in acid to remove these impurities.
Oxidation treatment:
Put the cleaned CNC machined parts into an oxidizing agent, usually an alkaline chemical solution.
A chemical reaction is carried out at a certain temperature to form a black oxide film on the surface of the metal. This process is also known as blueing.
According to different temperatures and processing times, different types of black oxide films can be obtained, such as hot black oxidation and medium temperature black oxidation.
Post processing:
Including cleaning and neutralization steps to ensure the quality of the oxide layer.
If there are blind holes on CNC machined parts or assembly is required, it may be necessary to clean them again with alkaline solution to prevent leakage from damaging the surface of the parts.
The oxide layer can be treated with oil, wax, or paint to further enhance the surface’s anti-corrosion performance and glossiness.
2、 Principle
Black oxidation treatment is a chemical reaction between metals and oxygen elements in oxidant solutions, forming a dense black oxide film (such as ferric oxide, Fe3O4). This oxide film can isolate air and water, prevent oxidation and corrosion inside the metal.
3、 Type
Hot black oxidation:
Place CNC Machined Parts in a hot solution composed of sodium hydroxide, nitrite, and nitrate to transform the surface into magnetite (Fe3O4).
The processing temperature is usually high (such as 130-145 ℃), and the formed oxide film is thick and uniform.
Medium temperature black oxidation:
Similar to hot black oxidation, but with a lower processing temperature (90-120 ℃).
Suitable for scenarios with high environmental requirements, as lower temperatures can reduce the generation of corrosive gases.