Black Oxide Surface Finish Supplier In China
Black Oxide, also known as blackening or gun bluing, is a chemical conversion coating that forms a thin layer of magnetite (Fe₃O₄) on the surface of ferrous metals. This process provides mild corrosion resistance and minimizes light reflection, making it a popular choice for tooling, fasteners, and various machinery components. As an experienced industrial supplier in China, Celerity Precision offers a reliable and consistent black oxide finish. We deliver parts with a clean, dark appearance and preserved dimensional integrity, often sealed with oil for enhanced protection right out of the box.
For a functional, dimensionally stable, and cost-effective black finish on your steel parts, choose Celerity Precision as your supplier.
Your Black Oxide Finish Manufacturer
At Celerity Precision, we are a manufacturer that integrates black oxide finishing as a key part of our in-house capabilities for steel components. Our blackening line involves a series of controlled immersion tanks, including cleaning, rinsing, oxide conversion, and a final sealant bath (typically oil or wax). We meticulously control the temperature and chemical concentration of the hot alkaline salt bath to ensure the formation of a deep, uniform black finish without the risk of hydrogen embrittlement. This level of process control guarantees consistent results from the first part to the thousandth.
As your direct manufacturing partner, we understand the entire lifecycle of your component. We machine your parts to precise specifications and then seamlessly transition them to our finishing department. This one-stop-shop approach eliminates logistical hassles and ensures total accountability for the final product. We can advise when black oxide is the most suitable finish for your application and ensure all parts are properly cleaned and prepared for a durable, well-adhered finish. Trust Celerity Precision to manufacture parts that are not only accurately machined but also professionally finished and ready for assembly.
Get your steel components machined and finished under one roof. Upload your design files to Celerity Precision for a fast, integrated quote.
Black Oxide: Technical Specifications
| Feature | Description |
| Surface Roughness (Ra) | No Impact. Black oxide is a conversion coating with negligible thickness. It does not alter the surface roughness or texture of the original machined part. |
| Applicable Materials | Primarily for ferrous metals: Carbon Steel, Alloy Steel, and Stainless Steel. The process varies slightly for stainless steel to achieve the black finish. |
| Cosmetic Availability | Good Functional Aesthetic. Provides a clean, uniform, non-reflective black finish. It is not a high-end cosmetic finish and can show variations in luster depending on the underlying surface. |
| Visual Appearance | A deep, rich black color. The finish can range from matte to semi-glossy, largely depending on the smoothness of the underlying material. It is typically sealed with oil, giving it a slight sheen. |
Advantages of Black Oxide Surface Finish
Virtually No Dimensional Change
With a coating thickness of less than 1 micron, it is an ideal finish for high-precision, tight-tolerance parts and threads.
Cost-Effective Corrosion Protection
Provides a good level of mild corrosion resistance, especially when sealed with oil, at a lower cost than painting or plating.
Reduced Light Glare
The dark, non-reflective surface is perfect for optical components, tooling, and military applications where minimizing reflection is crucial.
Decorative Black Finish
Offers an attractive, classic black appearance for a wide range of industrial and commercial products.
No Hydrogen Embrittlement
Unlike some plating processes, the black oxide process does not induce hydrogen embrittlement, so the strength and integrity of the base metal are unaffected.
Improved Lubricity
The optional oil or wax sealant provides lubricity, preventing galling on threaded components and moving parts.
Black Oxide Design Considerations
Mild Corrosion Resistance
The finish only offers minimal protection on its own. It must be kept oiled or waxed to be effective against rust, especially in humid environments. It is not suitable for severe outdoor or marine applications.
No Increased Hardness
The black oxide layer is a soft iron oxide and does not increase the hardness or abrasion resistance of the part.
Surface Preparation
The final appearance is directly influenced by the pre-finish condition. A smooth, polished part will result in a glossy black finish, while a matte machined part will result in a matte black finish.
Welds and Heat Treatment
Welded areas or parts that have been heat-treated may result in a slightly different color or appearance after blackening due to changes in the surface metallurgy.
FAQ
Is black oxide a type of paint or plating?
Neither. It is a chemical conversion process that changes the immediate surface of the steel into black iron oxide (magnetite). Nothing is deposited onto the part.
How much size does black oxide add?
Essentially zero. The dimensional change is so minimal (less than a micron) that it is considered a “no build-up” finish, perfect for threaded parts.
How much rust protection does it offer?
On its own, very little. The corrosion resistance comes from the sealant (oil, wax, or lacquer) applied after the blackening process. With regular oiling, it offers good indoor corrosion protection.
Can you black oxide aluminum or brass?
No, the standard hot black oxide process is only for iron-based metals like steel and stainless steel. Different chemical processes are used to blacken other metals.
Will the black finish rub off?
The black oxide layer itself is integral to the steel and very durable. However, the protective oil sealant can be wiped off and should be reapplied periodically to maintain corrosion resistance.
Does black oxide affect the hardness of the part?
No, it is a low-temperature process and does not change the mechanical properties, such as hardness or strength, of the base metal.
Is it the same as "gun bluing"?
Yes, gun bluing is a traditional term for the black oxide process used in the firearms industry.
Can you weld a part after it has been black oxidized?
No, the finish and oil sealant must be completely removed from the area before welding to ensure a proper weld.
Why should I choose black oxide over painting?
Choose black oxide when you need a black finish but cannot tolerate the dimensional build-up of paint, such as on fasteners, gears, or other precision-fit components.
How do I specify black oxide on my drawing?
A typical note is “Finish: Black Oxide and Oil per MIL-DTL-13924, Class 1.” If you are unsure, simply stating “Finish: Black Oxide and Oil” is sufficient for most applications.