High Strength Bolts Grade 12.9

High Strength Bolts Grade 12.9 — Premium Quenched & Tempered Alloy Steel | M6–M30

Grade 12.9 high strength bolts represent the highest standard metric strength grade, delivering a minimum tensile strength of 1220 MPa and yield strength of 1100 MPa. Manufactured from premium alloy steel (42CrMo / SCM440 / 35CrMo), these bolts are engineered for the most demanding applications requiring maximum strength-to-size ratio. Each bolt undergoes controlled quenching and tempering, hydrogen embrittlement relief, and 100% hardness testing to ensure zero-defect performance.

Material & Specifications

Size Range	M6 to M30 / 1/4″ to 1-1/4″
Standard	ISO 898-1, DIN 912 (socket head), DIN 931/933 (hex head), GB/T 3098.1
Material	Premium Alloy Steel — 42CrMo (SCM440), 35CrMo (SCM435), 20MnTiB
Surface / Coating	Dacromet (recommended for 12.9), Black Oxide, Phosphating, Multi-Element Alloy Co-Permeation
Tensile Strength	≥ 1220 MPa (Grade 12.9)
Yield Strength	≥ 1100 MPa
Hardness	385-435 HV (HRC 39-44)

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

• Highest metric strength grade — 1220 MPa minimum tensile strength
• Controlled quench and temper process with full heat treatment documentation
• Mandatory hydrogen embrittlement relief baking after any plating process
• 100% hardness testing and ultrasonic crack detection available
• Dacromet coating recommended to eliminate hydrogen embrittlement risk
• Premium alloy steel with verified Jominy hardenability curves

Applications

• Automotive engine and transmission critical fastening
• Aerospace and defense equipment (with special certification)
• Hydraulic cylinder and high-pressure system assembly
• Heavy-duty machinery and equipment requiring compact high-strength joints
• Motorcycle and performance vehicle critical connections
• Precision machinery and tooling applications

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