Black oxidation is a kind of chemical surface treatment. it can produce an oxide film on the metal surface to isolate the air and avoid rusting. Black oxidation is used for surface coating commonly because it can eliminate reflections.

How does Black Oxidation work?

When put steel parts in chemical solution and heat them to a certain temperature, the surface of steel parts will be oxdized and form a smooth and dense oxide film. this is how the Black Oxidation work. The name of this oxide film is Fe3O4, it can effectively protect the steel parts from rust.

There are two Black Oxidation methods today. One is to use alkaline heating to blacken the metal surface, it is used for high carbon steel. One is to use normal temperature blackening, it is commonly used for low carbon steel with a good result.

What material can be Black Oxide?

Black oxidation treatment is often used to treat industrial parts such as bolts, nuts, springs, metal covers, etc., as well as metal tableware, furniture and other daily necessities.

One of the commonly used solvent ratios:

  • Copper sulfate 2g/L
  • selenite 4g/L
  • sodium molybdate 2g/L
  • sodium thiosulfate 1g/L
  • nickel sulfate 4g/L
  • pH 1.5~2.5
  • time 5~8min

Advantages of black oxidation

  • No need to use electric heating, saving energy
  • Short process time and improved work efficiency
  • Low cost, simple equipment, and easy operation
  • This process has strong adaptability and can blacken ductile iron.
  • It improve the aesthetics of metal products and present a high-quality, low-key, and luxurious visual effect.
  • It can form an oxide film on the metal surface to increase the anti-corrosion ability of metal products.

Disadvantages of black oxidation

  • the thin oxide film can be worn during use or affected by environmental factors such as humidity, causing oxidation.
  • Once the surface is scratched or worn, it will be difficult to repair.
  • the acid-base solutions and other chemicals will cause pollution to the environment.

Applications of black oxidation

Electronic parts

It can be used to process metal casings, buttons, speakers, and other components, meet people’s gradually increasing appearance requirements.

Automotive parts

Automotive parts such as Vehicle frames, engine casings and gearboxes with Black oxidation can save costs and improve product durability


Black oxidation can be used to treat metal furniture, dining tables, chairs and other parts. it can make the parts get a good appearance and quality.


Black oxidation Can be used to handle metal tableware, cooking utensils, lunch boxes and more.

Mechanical parts

Mechanical parts such as fasteners, bolts, nuts and metal covers with Black oxidation can improve their corrosion resistance.

Tips for the black oxidation process

  • Take out the parts Only when it is completely black . Black oxidation time can not be too long, otherwise the film will be loose.
  • The blackening time can be adjusted according to the actual situation. The blackening time should be longer in winter and shorter in summer.
  • After the workpiece is taken out from the liquid solution, it should stay for some minutes to continue the film-forming reaction and increase the bonding force.
  • The workpiece can be put back into the chemical liquid solution until it is done perfectly If you found it is not evenly colored.


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