What is black oxide coating? In this article, we’ll take a look at black oxide as a surface finish, its history, common applications, and more
A brief history of black oxide
The exact origin or inventor of black oxide coating is not well documented, but the process of blackening iron and steel has been used by blacksmiths and metalworkers for centuries. It was, and still is, seen as a complete or partial solution to various challenges.
What were the early uses of black oxide coating?
- Prevent corrosion. Black oxide coating helps improve the resistance of metal components to corrosion and rust, extending their life and reducing the need for expensive or time-consuming repairs or replacement.
- Reduces wear. Black oxide increases the hardness and durability of metal surfaces, reducing wear and improving the performance of metal components in harsh or industrial environments.
- Aesthetics. With a smooth, matte finish, Black Oxide improves the appearance of metal components, making them easier to integrate into a variety of applications where visibility is not an issue.
- Reduced light reflection. For a variety of functional and cosmetic applications, a black oxide coating makes surfaces less reflective.
What is black oxide predominantly used for now?
Black oxide is still used to achieve the above results and is well suited for applications that require a durable, low maintenance, corrosion resistant finish such as
- Fasteners, hardware and tools. Black Oxide is a popular finish for fasteners such as screws, nuts, bolts, hand tools and other hardware as it provides a matt, aesthetically pleasing finish that is corrosion resistant, durable and easy to grip.
- Automotive and aerospace components. In the automotive and aerospace industries, black oxide is used as a surface finish for a variety of parts, including engine components, suspension systems and landing gear.
- Industrial equipment. People use Black Oxide to finish a wide range of industrial equipment, such as pumps, valves, and machinery, to provide corrosion and wear-resistant surfaces.
How does black oxide work?
Black Oxide is a finishing process that involves immersing a part in a solution containing sodium hydroxide and potassium nitrate. At Protolabs Network, the application of black oxide is a six-step process in which a part is
- Machined and deburred
- Cleaned with alkaline solutions
- Rinsed in water
- Black oxidised by immersion in a hot (135-145ºC) alkaline bath for a period of five to 40 minutes, depending on the size of the part.
- Rinsed again in water
- Finished with oil, varnish or wax to seal the oxide surface
Black Oxide Coating Best Practices
Follow these tips and note some design limitations for black oxide coatings.
- Complex geometries. Parts with complex geometries and tight corners may not be suitable for black oxide, as it can be difficult to achieve a uniform coating on these surfaces.
- Surface finish. Black Oxide works best on surfaces with a smooth, uniform finish, as rougher surfaces can result in a less uniform coating.
- Material compatibility. Not all metals are compatible with the black oxide process. Some metals, such as aluminium, do not react well to the black oxide process, which can result in a poor quality finish.
- Corrosion resistance. While black oxide provides some protection against corrosion, it is not as effective as other finishes such as anodising or electroplating.
- Masking. Black Oxide does not have a significant dimensional effect, so there is no need to mask parts.
Sourcing Simplified – Start Your Next Project With PROTO MFG
Are you looking for a reputable partner for your parts fabrication and machining projects? Look no further. At PROTO MFG, we specialize in CNC machining and related technologies, including sheet metal fabrication, rapid prototyping, etc. Whether it is a project with a simple design or parts with complex geometries, do not hesitate to contact us today!
