ASTM A325 Structural Bolts

ASTM A325 Structural Bolts — Heavy Hex Structural Bolts for Steel Construction | 1/2″–1-1/2″

ASTM A325 structural bolts are heavy hex head bolts designed specifically for structural steel connections in building and bridge construction. Manufactured to ASTM A325 specification (now technically superseded by ASTM F3125 Grade A325), these bolts feature a shorter thread length than standard bolts, ensuring that the unthreaded shank spans the shear plane for optimal performance. Available in Type 1 (medium carbon steel) and Type 3 (weathering steel) variants.

Material & Specifications

Size Range	1/2″ to 1-1/2″ (M12 to M36 equivalent)
Standard	ASTM A325 / ASTM F3125 Grade A325, AISC 360
Material	Type 1: Medium Carbon Steel; Type 3: Weathering Steel (Cor-ten compatible)
Surface / Coating	Black/Plain (standard), Hot-Dip Galvanized (ASTM F3125 Grade A325 Type 1 galvanized), Dacromet
Tensile Strength	≥ 827 MPa (120 ksi) for ≤ 1″; ≥ 724 MPa (105 ksi) for > 1″
Yield Strength	≥ 635 MPa (92 ksi)
Head Type	Heavy hex head (1.5x standard hex head dimensions)

Surface Treatment & Zinc Coating Quality

At BoltNutsPlus, we understand that surface treatment is critical to fastener longevity and performance. Our products undergo rigorous coating processes to ensure maximum corrosion resistance and durability. We offer five premium coating options, each tested to international standards:

• Hot-Dip Galvanizing (HDG) — Thick zinc layer (50-120μm) providing superior long-term corrosion protection for outdoor, marine, and industrial environments. Compliant with ISO 1461 / ASTM A153 standards. Salt spray resistance: 500-1,000+ hours. Ideal for structural steel assemblies exposed to harsh weather.
• Electroplated Zinc Blue-White (Zn Blue/White) — Bright, clean silver-blue appearance with 5-15μm zinc layer. Cr3+ passivation technology, fully RoHS compliant. Ideal for indoor machinery, electronics, and general-purpose applications requiring aesthetic appeal and moderate corrosion resistance.
• Color Zinc / Yellow Zinc (Iridescent Passivation) — Multi-colored iridescent passivation film offering enhanced corrosion resistance (100-200 hours salt spray) with a distinctive golden finish. Widely preferred in automotive, agricultural equipment, and construction machinery sectors for its balanced protection and visual appeal.
• Dacromet Coating — Advanced water-based zinc-chromium coating technology with NO hydrogen embrittlement risk. Provides 1,000+ hours salt spray resistance, making it the preferred choice for high-strength fasteners in extreme environments. Environmentally friendly (no heavy metal discharge), RoHS/ELV compliant, ideal for automotive and wind energy applications.
• Multi-Element Alloy Co-Permeation — Zinc-aluminum-rare earth alloy layer offering 2-3x the corrosion resistance of traditional galvanizing. Features self-healing properties at scratch points, ensuring long-term protection even in damaged areas. Ideal for critical infrastructure, power transmission towers, coastal projects, and marine installations.

Key Features

• Heavy hex head provides larger bearing surface and wrenching area for structural applications
• Shorter thread length ensures unthreaded shank spans the shear plane
• Type 3 weathering steel variant develops protective oxide layer for atmospheric corrosion resistance
• Designed for use with ASTM F436 hardened washers and ASTM A563 heavy hex nuts
• Tension-control bolt option available for RCSC (Research Council on Structural Connections) compliance
• Full certification package: mill test reports, heat treatment records, lot traceability

Applications

• Structural steel building construction — beam-to-column connections
• Bridge construction and infrastructure projects
• Industrial facility and warehouse steel framing
• Power plant and refinery structural steel
• Stadium, arena, and large-span roof structures
• Seismic-resistant moment frame connections (with pre-tensioning)

Why Choose BoltNutsPlus?

• ISO 9001:2015 Certified Manufacturing — consistent quality you can trust on every batch
• 15+ Years of Export Experience — serving 40+ countries across 6 continents
• Full Traceability — material certificates (EN 10204 3.1) and comprehensive test reports included
• Custom Packaging & OEM/ODM — your brand identity, your specifications, our precision manufacturing
• Third-Party SGS / Bureau Veritas Inspection Available upon request
• 24-Hour Quote Response — same-day reply for urgent requirements; standard 24-hour turnaround