What Is a Black Oxide Coating Services?
Black Oxide Coating Services is a surface treatment method for metals to prevent rust.
The surface is oxidized by boiling the metal in an alkaline solution to form a black film. Black Oxide Coating Services is mainly used for rust prevention on steel parts.
The advantage of Black Oxide Coating Services is that the film is very thin and there is little change in the dimensional accuracy of the original metal. It has excellent wear resistance and retention properties, and is environmentally friendly as there is no need to dispose of the chemical solution. Another advantage is that it is a rust-preventive treatment at a lower cost than the plating process.
On the other hand, the disadvantage of Black Oxide Coating Services is that it can only be done in black color due to the characteristics of the chemical solution. As with plating or painting, it is basically impossible to match the color with other parts. It is also important to note that a rust inhibitor must be applied to maintain the rust-preventive properties.
Uses of Black Oxide Coating Services
Black Oxide Coating Services are used to improve corrosion resistance, enhance appearance, and prevent reflection.
1. Improvement of Rust-Preventive Properties
The essential use of Black Oxide Coating Services is to improve corrosion resistance by creating a black film. In addition to the fact that dimensional accuracy remains almost the same before and after processing, the processing cost is relatively low, making it suitable for a wide range of applications.
2. Improvement of Appearance
The soothing black color produced by Black Oxide Coating Services gives a luxurious feel and is used to enhance design. It is used not only for industrial products, but also for interiors and artwork.
3. Anti-reflection
Since black processed metal parts are less shiny, they are used to prevent reflections. By preventing light reflection on visible parts such as manufacturing machinery, it is possible to alleviate stress on workers.
4. Improved Lubricity
Black Oxide Coating Services improves the abrasion resistance of steel materials, and the rust inhibitor also improves lubricity.
Principle of Black Oxide Coating Services
In Black Oxide Coating Services, steel is placed in an alkaline solution containing caustic soda and heated to 140-150°C for 15-20 minutes to cover the surface with black rust. The component of this black rust is tri-iron tetroxide (Fe3O4), which is a stable passive film. This prevents red rust from forming on the steel and improves its rust-preventing properties.
Black Oxide Coating Services is a process that has little effect on dimensional accuracy because the thickness of the coating is only 1-2 µm. It is a chemical reaction treatment of the surface and will not peel off like plating or painting. Another advantage is that it is wear-resistant and oil-impregnated. The porous surface retains the rust inhibitor.
Black Oxide Coating Services has the advantage of low heating temperature, which has little effect on material strength and material properties.
Types of Black Oxide Coating Services
Black Oxide Coating Services is sometimes called “black plating,” but the basic method and finish are the same. Similarly, the processing methods called “ferumite treatment,” “SOB treatment,” and “alkali treatment” are not different from Black Oxide Coating Services.
Although there are differences in the color tone depending on the chemical formulation and facilities used, Black Oxide Coating Services itself is not classified into different types.
Other Information on Black Oxide Coating Services
Chemicals Used in Black Oxide Coating Services
Chemicals are used in each stage of Black Oxide Coating Services.
1. degreasing process
In the degreasing process, water-soluble alkaline degreasing agents are used. It is a water-soluble degreasing and cleaning agent with nonionic surfactant, nonflammable, and odorless. It has strong degreasing and cleaning power equivalent to that of chlorine compound solvents. When draining, use dilute sulfuric acid for neutralization due to its low alkali concentration.
2. Rust removal process
Rust removal is performed using an iron rust and scale remover. The agent is hydrochloric acid to which is added an acid that promotes rust and scale removal, a surfactant that stabilizes the agent, and an inhibitor that prevents hydrogen embrittlement and over-peeling.
3. black dyeing process
A heated black staining agent is used to cover the steel with a jet-black iron tetroxide film. Castings and special steels, which tend to have a reddish tinge, can be finished in jet black. The agent conforms to U.S. Department of Defense MIL standards, U.S. aerospace material standards, International Organization for Standardization standards, German industrial standards, etc.
4. Rust Prevention Process
After the blackening process, a corrosion inhibitor is used. This medium-term rust inhibitor has excellent water displacement properties and is suitable for rust inhibiting treatment on wet parts and in humid environments. The estimated period of rust inhibiting is 6 to 12 months.