ASTM F2329 – Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware

ASTM F2329 is the standard specification for applying hot-dip zinc coatings to iron and steel hardware such as bolts, nuts, washers, anchors, and threaded rods. It ensures corrosion resistance, thread functionality, and long-term durability for hardware used in construction and industrial environments.

Purpose and Scope

This standard defines the requirements for hot-dip galvanizing, including coating thickness, surface appearance, adhesion, and overtapping for threads. It is widely used for hardware that will be exposed to weather, moisture, or corrosive environments.

Key Features

• Hot-Dip Process: Hardware is cleaned, fluxed, and dipped in molten zinc (~450°C), forming a protective metallic bond.
• Minimum Coating Thickness: Varies by size and type (e.g., 43–54 μm average for bolts and washers).
• Thread Fit: Internal threads (nuts) must be overtapped to ensure smooth assembly with coated bolts.
• Hydrogen Embrittlement Protection: Since it’s not electroplated, F2329 coating avoids embrittlement, making it safe for high-strength bolts.
• Acceptable Finish: Minor roughness or discoloration is allowed as long as it doesn’t affect function.

Comparison with Other Coating Standards

Applications

• Steel buildings and bridges
• Industrial foundations and anchor systems
• Utility poles and substations
• Guardrails, towers, and signage
• Marine and coastal construction

Conclusion

ASTM F2329 ensures high-performance protection for fasteners exposed to harsh conditions. It is essential for bolt manufacturers and contractors aiming for long-term reliability, safety, and compliance in structural and infrastructure projects.