Precision surface finishing
Black Oxide Coating Services for CNC Parts
Weldo provides controlled black oxide coating for CNC-machined steel, stainless steel and other compatible metal parts.
Minimal buildup
Supports close fits and functional threads.
Sealer choices
Oil, wax or dry-to-touch options.
Controlled process
Hot and stainless-grade routes.
Final inspection
Appearance and critical dimensions checked.
Process selection
Which Black Oxide Process Is Right?
We select the process according to material grade, heat-treatment condition and drawing specification.
Hot Black Oxide
About 135–150°C for steel, tool steel and compatible cast iron.
Mid-Temperature
About 90–120°C for approved industrial applications.
Rostfreier Stahl
Dedicated chemistry matched to the stainless grade.
Room-Temperature
Used for approved local color restoration and touch-up.
Controlled workflow
How Is Black Oxide Applied?
Five controlled stages connect drawing requirements with a consistent finished part.
Suitable materials
Black Oxide Compatible Materials
The material grade and surface condition determine the process, masking and sealing route.
Kohlenstoffstahl
Pins, sleeves, brackets and screws.
Legierter Stahl
Gears, shafts, bushings and high-strength fasteners.
Werkzeugstahl
Punches, dies and tool holders.
Gusseisen
Gears, pulleys and housings.
Rostfreier Stahl
Instrument parts, optical hardware and fasteners.
Powder-Metal Parts
Sintered gears, sprockets and bushings.
Aluminum normally uses black anodizing. Copper and brass require dedicated chemical blackening and should be specified separately.
Drawing requirements
Black Oxide Drawing Requirements
State the substrate, standard revision, process class, sealer, treatment area, masking area and inspection method.
| Standard | Main application | What to specify |
|---|---|---|
| MIL-DTL-13924F | Black conversion coatings for ferrous metals | Class, preservative treatment and inspection |
| SAE AMS2485M | Engineering and aerospace black oxide | Material condition and acceptance |
| ISO 11408:1999 | Cast iron, carbon, low-alloy and stainless steel | Substrate, protection and testing |
| DIN 50938:2025-06 | Immersion black oxide on ferrous parts | Substrate and inspection |
| SAE AMS2489B | Color restoration after oxide removal | Touch-up area and visual acceptance |
For hardened steel at 39 HRC or above, confirm the specified stress-relief and hydrogen-embrittlement relief requirements before production.
Appearance and sealing
Black Oxide Sealer Options
The original surface and selected sealer determine the final shade, gloss and storage protection.
Oil Seal
For gears, shafts, tools and lubricated parts.
Wax Seal
For a drier handling surface.
Dry-to-Touch Seal
When oil transfer must be limited.
Unsealed
When another coating or bonding step follows.
Leistung
Benefits of Black Oxide
Minimal dimensional change
Supports threads, bores, shafts and close fits.
Low-reflective appearance
Reduces glare on tools and internal components.
Preserved texture
Retains the original polished, ground or blasted texture.
Light corrosion protection
Sealing supports storage and controlled indoor use.
Lubricant retention
Oiled surfaces retain lubricant on sliding contacts.
Base properties preserved
Strength and hardness remain controlled by the substrate.
Finish comparison
Black Oxide vs. Black Zinc
Choose black oxide for minimal buildup and low glare. Choose black zinc for stronger sacrificial corrosion protection.
| Key difference | Schwarzes Oxid | Black zinc |
|---|---|---|
| Formation | Chemical conversion of the ferrous surface | Electrodeposited zinc with black passivation |
| Dimensional buildup | Negligible in normal processing | Measurable thickness as specified |
| Korrosionsschutz | Light duty with suitable sealing | Higher sacrificial protection |
| Typische Bauteile | Tools, gears, shafts and fixtures | Exposed fasteners and brackets |
Masking and fit
What Should Be Masked?
Masking protects surfaces where oxide or sealer could affect the next operation.
Functional areas
Threads, precision bores, sealing faces and electrical contacts.
Process boundaries
Bonding, welding, vacuum and customer-specified bare areas.
Acceptance check
Black Oxide Defects and Inspection
Weldo checks coverage, appearance, sealing, cleanliness and critical dimensions before shipment.
| Fehler | Inspection focus |
|---|---|
| Uneven color | Material, cleaning, bath and surface texture |
| Rust stains | Rinsing, sealing and packaging |
| Bare areas | Oil, scale, activation and rack contact |
| Smut or residue | Reaction control and rinsing |
Custom parts
Common Black Oxide Parts
Black oxide suits precision ferrous-metal parts that need a dark finish with minimal buildup.
Machinery & Automation
Locating pins, guide shafts, couplings and fixtures.
Automotive & Transmission
Gears, splined shafts, bushings and washers.
Tooling & Molds
Punches, dies, holders and fixture components.
Optical & Instruments
Lens mounts, adjustment rings and internal supports.
Fasteners & Hardware
Bolts, nuts, screws, washers and retaining rings.
Industrielle Ausrüstung
Brackets, control parts and internal mechanisms.
Frequently asked questions
Black Oxide FAQs
Which black oxide standard should be specified on a drawing?
Specify the standard and revision together with the substrate, process class, sealer, treated area and inspection requirements.
Can Weldo mask threads and precision bores?
Yes. Threads, bores, sealing faces, electrical contacts and other functional areas can be masked according to the drawing.
Which sealer should be used?
Oil suits lubricated parts, wax provides a drier handling surface, and dry-to-touch sealer limits oil transfer.
How are black oxide parts inspected?
Weldo checks coverage, color, sealing, cleanliness and critical dimensions. Reports and additional testing are available when specified.
Can black oxide be combined with CNC machining?
Yes. CNC machining, masking, black oxide processing, cleaning and final inspection can be coordinated in one production route.
Welche Angaben werden für ein Angebot benötigt?
Send the drawing, material grade, quantity, finish requirement, critical dimensions, masking areas and delivery target.
Senden Sie Ihre Zeichnung
Get a Black Oxide Quote
Weldo will review the material, masking, process specification, inspection scope and delivery schedule.