Black Oxide

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Black Oxide

Definition and Function

Black oxide is a common metal surface treatment that creates a dense black oxide layer on the surface of steel and other ferrous alloys through a chemical reaction.
This layer provides limited corrosion resistance, reduces light reflection, and offers basic rust protection.
Compared with other coating methods, the oxide layer is very thin and does not significantly alter part dimensions, making it suitable for precision components.

Colors

Black

Dark Gray

After black oxide treatment, the surface of the workpiece exhibits a uniform black or dark gray appearance.

The shade of black may vary slightly depending on the base material and process conditions.

Example of a bead-milled + anodized colored part

Technical Properties

Applicable Materials	Burrs and Sharp Edges	Appearance	Tolerance
Primarily steel and ferrous alloys	Removed	Uniform black or dark gray finish with anti-glare properties	Due to the extremely thin coating (typically 0.5–1.5 μm), dimensional accuracy is virtually unaffected

Applicable Materials

Metals: Stainless Steel Mild Steel Alloy Steel Tool Steel Spring Steel 　

Process Characteristics

During processing, the workpiece is immersed in a specialized alkaline oxidizing solution, forming a thin oxide layer on the surface.

Since the oxide layer alone has limited corrosion resistance, it is typically supplemented with rust-preventive oil or sealant to enhance protection.