Precision Fastener Black Oxide Finishing Project

Black Oxide Fastener 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 thread accuracy after black oxide finishing. The customer’s precision fasteners required black oxide treatment while maintaining critical thread dimensions and assembly performance. Excessive dimensional change after finishing could affect fastening accuracy and installation reliability.
Improving corrosion resistance of steel fasteners. The carbon steel fasteners were used in industrial equipment where long-term corrosion protection was required. The customer needed a surface treatment solution that could improve corrosion resistance without affecting the original mechanical properties.

03 / Our Solution

Using our black oxide finishing process — a chemical conversion coating technology that forms a uniform oxide layer on steel surfaces — we improved corrosion resistance and surface stability while minimizing dimensional impact on precision fasteners.

Process Adjustments

Precision-controlled black oxide conversion process

The black oxide process parameters were optimized to ensure uniform oxide layer formation while maintaining thread dimensions and mating accuracy.

Surface preparation optimization

Controlled pre-treatment procedures were applied to improve surface activation and ensure consistent black oxide layer formation across each fastener.

Batch Quality Verification

Sampling inspections were conducted to verify:

Black oxide layer consistency
Thread dimensional stability
Surface appearance uniformity

Project Results

Metric	Before	After Chiheng Solution	Improvement
Dimensional change after finishing	~5–8μm	<2μm	~70% reduction
Salt spray resistance	Rust visible at 24 hours	No rust after 96 hours	4× improvement
Thread assembly performance	Occasional fitting issues	100% assembly pass	Improved reliability

The same controlled black oxide process can also support precision gear applications requiring dimensional stability and corrosion protection. See our precision gear black oxide finishing case study.

Client Testimonial

“Chiheng’s black oxide finishing solution helped us maintain fastener precision while achieving the corrosion protection required for industrial applications.”
— Jalene, Purchasing Specialist, Industry peer

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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