Precision Gear Black Oxide Finishing Project

Project Overview

Project Info	Project Results
Client: A precision machinery manufacturer	✅ Dimensional stability: <2μm change after black oxide finishing
Project: Black oxide finishing for precision carbon steel fasteners	✅ Corrosion resistance: 96-hour salt spray test with no rust
Volume: 5,000 pcs per batch	✅ Thread assembly performance: 100% assembly pass rate
Material: 45# carbon steel precision fasteners	✅ Surface consistency: Uniform black oxide finish across the production batch

Client Challenge

Maintaining gear accuracy after surface treatment. The customer’s precision gears required black oxide finishing while maintaining critical dimensions and tooth profile accuracy. Any excessive dimensional change could affect gear meshing performance during assembly.
Improving long-term corrosion protection. The gears required reliable surface protection during transportation, storage, and equipment operation. Previous surface protection methods could not provide sufficient rust resistance for long-term use.
Ensuring batch consistency for production assembly. The customer required consistent surface appearance and stable processing quality across 2,000 precision gears to ensure smooth assembly into mechanical systems.

03 / Our Solution

Using our black oxide finishing process — a chemical conversion process rather than a deposited coating — we provided corrosion protection while minimizing dimensional impact on precision gear components.

Process Adjustments

Controlled Black Oxide Processing Parameters

The oxidation temperature and treatment duration were optimized to achieve a uniform conversion layer on gear surfaces while maintaining dimensional stability.

Enhanced Post-Treatment Sealing

A dual sealing process was applied to improve corrosion resistance during storage and transportation:

Rust-preventive oil
Wax sealant

Batch Quality Verification

Controlled sampling inspection was performed to verify:

Gear dimensional stability
Surface appearance consistency
Black oxide treatment uniformity

Project Results

Metric	Before	After Chiheng Solution	Improvement
Dimensional change	~5–8μm	<2μm	~70% reduction
Salt spray resistance	Rust visible at 24 hours	No rust after 96 hours	4× improvement
Batch surface consistency	Variation between batches	Uniform finish across production batch	Improved consistency

Our black oxide finishing process is also applied to precision fasteners where thread accuracy and assembly reliability are critical. See our precision fastener black oxide finishing case study.

Struggling with small parts that can't be individually fixtured for anodizing?

If your parts require a different surface treatment altogether — for example, corrosion protection on steel components — our black oxide finishing service addresses similar small-part handling challenges for carbon steel, alloy steel, and select stainless grades.

🔗 Explore our anodizing service | 🔗 How surface finishing affects tolerances

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