Black Oxide surface finish
Black Oxide applied by YiguProto

Surface finish

Black Oxide for CNC & Molded Parts

Black oxide is a deep black finish for steel and copper. It adds mild corrosion resistance and a clean, professional look.

  • Uniform matte black with no thickness build-up.
  • Great for tools, fasteners, and hardware.
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What it is

What Is Black Oxide?

Black oxide (blackening) is a chemical process. Steel or copper parts are dipped in a hot bath that forms a thin iron oxide layer. The part stays its original size. The finish is matte black and is often oiled afterward to boost rust protection.

Black oxide adds almost no thickness, so it is safe for threaded and tightly fitted parts.

How it works

How Black Oxide Works

Clean & degrease

We remove oil and scale from the surface.

Prioritize (optional)

A light acid prep improves uniformity.

Black oxide bath

The hot alkaline bath converts the surface to black iron oxide.

Rinse & oil

We rinse, then apply oil or wax to seal and protect.

After oiling, the finish resists fingerprints and light corrosion. For more protection we can add a rust-preventive topcoat.

Why choose it

Benefits of Black Oxide

Uniform black

Clean, consistent matte appearance.

No size change

Adds only sub-micron thickness.

Mild corrosion resistance

Oiled finish resists rust in indoor use.

Low friction base

Works well under oil for moving parts.

Professional look

Popular for tools and hardware.

Typical specs

Typical Black Oxide Specifications

SpecificationTypical range / valueNotes
Base materialsSteel, stainless steel, copper, brass
Coating thickness0.5 – 2.5 µm
ColorMatte black
Post-treatmentOil or wax seal

Best applications

When to Use Black Oxide

Hand tools

Wrenches, clamps, and fixtures.

Fasteners

Screws, bolts, and shafts.

Firearms parts

Receiver and hardware components.

Precision shafts

Sliding parts that need no size change.

Materials

Compatible Materials for Black Oxide

We apply Black Oxide to the materials below. Not sure if your material qualifies? Our engineers will confirm it for free.

Carbon steelAlloy steelStainless steelCopperBrass

Our solution

Our Black Oxide Solution

We black-oxide steel and copper parts with a consistent matte finish. We add oil or a rust-preventive seal to match your environment.

  • Hot black oxide for uniform, durable color.
  • Oil or wax seal for indoor corrosion resistance.
  • Optional rust-preventive topcoat for harsher use.
  • Combined with CNC machining in one order.
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For outdoor or wet use, we recommend a clear protective topcoat over the black oxide.

Design tips

Design & DFM Tips for Black Oxide

Mask threads if needed

Tight threads may need masking.

Add a topcoat outdoors

Bare black oxide is best indoors.

Expect sheen change

Oil gives a slightly glossy look.

FAQ

Black Oxide — Frequently Asked Questions

Send your drawings or 3D files. Most quotes come back within a few hours on business days, never more than 24 hours.
Yes. All customer files and ideas are treated as confidential. We sign NDAs when needed.
Yes. Our engineers review your design and suggest changes that cut cost, improve quality, or speed up delivery.
For Black Oxide, we support one-off prototypes and full production runs. There is no strict MOQ.
We can make samples for your approval. Cost depends on the process, and it is credited back on a production order.
No. It adds less than a micron, so fits stay exact.
It gives mild protection. Oiled or topcoated parts resist rust better.
Yes, with a process suited to stainless.
Black oxide is thinner, conductive, and keeps tolerances; paint is thicker and insulating.

Need Black Oxide on your parts?

Send your files and get a finish recommendation + factory-direct quote.

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