Overview of Black Treatment

01 Definition

Blackening treatment is a process of turning metal surfaces (especially steel materials) black, also known as "oxide black" or "iron oxide protective film" treatment. This processing method mainly forms a dense black oxide film on the metal surface through chemical reactions, namely Fe3O4, thereby improving the appearance of the metal, enhancing corrosion resistance and wear resistance.

The main process methods for blackening treatment include:

1. Chemical method:

Acid washing method: Soak the metal in an acidic solution to remove the surface oxide layer and impurities, and then soak it in an alkaline solution to form an opaque oxide film on the metal surface, forming a black color.

Alkali washing method: Metal is added to an alkaline solution with an oxidant (such as sodium nitrate) and a reaction promoter, heated to an appropriate temperature (such as 130-150 ℃), to form a black oxide layer on the surface of the metal.

2. Physical Law:

High temperature oxidation method: Heating the metal to a high temperature causes an oxidation reaction on the metal surface, resulting in the formation of black oxide. This method is commonly used for metal materials such as iron and steel.

Wet electrochemical method: By applying current in a specific electrolyte, the metal surface undergoes an oxidation reaction to form black oxide. This method is commonly used for metal materials such as aluminum and copper.

03 Characteristics and advantages of blackening treatment:

1. Improve corrosion resistance: By forming a dense film of iron oxide, it effectively prevents internal corrosion of the metal.

2. Improve appearance: The treated metal surface presents a uniform black color with a certain decorative effect.

3. Maintain dimensional accuracy: Due to the fact that the changes on the metal surface during the processing are mainly caused by thin films formed by chemical reactions, the impact on the dimensions of the workpiece is relatively small.

4. Low cost: Compared with other surface treatment methods, blackening treatment has a lower cost and is suitable for large-scale production.

5. Simple process: The processing is relatively simple and does not require complex equipment or operational techniques.

04 Application Fields:

Common blackening treatment is widely used in various metal products and handicrafts, such as steel parts such as screws and bolts, precision mechanical parts, molds, automotive parts, decorations, and artworks. It not only improves the durability and aesthetics of the product, but also reduces production costs. Blackening treatment is an economical and effective method of metal surface treatment, which forms a dense black oxide film on the metal surface through chemical reactions, thereby improving the performance and appearance of the metal.