Black Oxide Hex Head Bolt with Nut and Washer is a high-strength, corrosion-resistant fastener solution designed for industrial-grade connections. Made of premium carbon steel with a uniform black oxide finish, this all-in-one kit eliminates the hassle of sourcing separate components, ensuring perfect compatibility, reliable clamping force, and long-term durability in dry to mildly corrosive environments.

Ideal for machinery assembly, structural steel, automotive, rail, and general engineering, our black oxide hex bolt sets meet strict DIN 931/DIN 933/ISO 4032 standards and are available in Grade 8.8, 10.9, and 12.9 for light to heavy-load applications.

• Chemical conversion finish forms a thin, adherent magnetite (Fe₃O₄) layer
• Corrosion resistance: protects against rust in dry/indoor and mildly humid environments
• Low reflection: reduces glare for precision or low-visibility applications
• Uniform black aesthetic: sleek, professional look for industrial and commercial use

• Grade 8.8/10.9/12.9 carbon steel, quenched & tempered for maximum strength
• Tensile strength: 800-1220 MPa; hardness: 22-44 HRC (varies by grade)
• Anti-deformation: withstands heavy shear and tension loads without bending or breaking

• Pre-matched components ensure perfect thread fit and consistent clamping
• Hex nut: DIN 934/ISO 4032, precision-machined for smooth engagement
• Flat washer: distributes load, prevents surface damage, and loosening
• Time & cost savings: no separate sourcing; ready for immediate use

• Thread standard: metric (M4-M30), coarse/fine pitch, Class 6g fit
• Head design: 6-sided hex for optimal torque transfer with standard wrenches
• Dimensional accuracy: ±0.02mm tolerance; 100% thread gauged
• Certifications: ISO 9001, SGS, RoHS compliant

• Machinery & equipment assembly
• Structural steel & construction
• Automotive & heavy-duty transport
• Rail & transportation infrastructure
• Furniture & general engineering

• 10+ years of fastener manufacturing experience; no middlemen
• Monthly capacity: 10,000+ tons
• Low MOQ: 1,000 pcs; OEM/ODM available for custom specs

• Raw material inspection -> heat treatment -> black oxide coating -> 100% dimensional check
• Third-party tested: SGS-certified for material, hardness, and corrosion resistance
• Consistent batch quality; reliable performance in critical applications

• Delivery time: 5-20 days after order confirmation
• Shipping ports: Tianjin, Qingdao, Shanghai; DDP/FOB/CIF available
• Multiple payment options: T/T, L/C, PayPal; volume discounts for bulk orders

• Custom lengths, grades, and packaging (boxes, cartons, pallets)
• Private labeling; custom black oxide shades or oiled finishes available

A1: Black oxide provides moderate corrosion resistance for dry/indoor and mildly humid environments. For coastal, chemical, or highly humid conditions, we recommend oiling or upgrading to hot-dip galvanized (HDG) finish.

A2: Higher grades offer greater tensile strength:

• 8.8: General-purpose, medium load (machinery, furniture)
• 10.9: Heavy load (structural steel, automotive)
• 12.9: Extreme load (heavy machinery, rail)

A3: Yes. We provide OEM/ODM services for non-standard lengths, thread pitches, and packaging. Contact us with your drawings or specs.

A4: Every batch undergoes raw material testing, heat treatment verification, coating inspection, and 100% dimensional checking. We provide SGS/ISO test reports upon request.

A5: Standard stock orders ship in 5-10 days; custom orders take 15-20 days. We prioritize urgent orders for key clients.