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FULLERKREG DIN 933 / GB 5783 Grade 8.8 full thread hex bolts with hot dip galvanising (HDG) combine reliable structural strength with the most durable zinc corrosion protection available for carbon steel fasteners. Manufactured from 10B21 or 35K medium carbon steel and hot dip galvanised to ISO 10684 / ASTM A153 standards, these bolts deliver a thick, metallurgically bonded zinc coating (45–100 μm) that provides decades of corrosion protection in outdoor, coastal, and aggressive industrial environments — far exceeding the performance of electroplated zinc coatings. The fully threaded shank ensures maximum thread engagement and grip-length flexibility. Compliant with DIN 933, GB 5783, and ISO 4017 standards.
| Property | Electroplated Zinc (CR3) | Mechanical Zinc Plating | Hot Dip Galvanised (HDG) — This Product |
|---|---|---|---|
| Coating Thickness | 5–12 μm | 15–25 μm | 45–100 μm ✅ |
| Bond Type | Electrochemical deposit | Mechanical impact | Metallurgical (Zn-Fe alloy layers) ✅ |
| Salt Spray Resistance | 72–200 hours | 200–500 hours | ≥ 1,000–2,000+ hours ✅ |
| Cathodic Protection | Limited | Good | Excellent — self-healing ✅ |
| Outdoor Service Life | 2–5 years | 5–10 years | 20–50+ years ✅ |
| Hydrogen Embrittlement Risk | Yes (electroplating) | Low | None (hot process) ✅ |
| Thread Tolerance Impact | Minimal | Minimal | Significant — threads re-tapped after galvanising |
| Appearance | Bright silver | Matte grey | Matte grey / spangled |
| Typical Application | Indoor / light outdoor | Automotive, light structural | Outdoor structural, infrastructure ✅ |
| Property | Grade 4.8 | Grade 8.8 — This Product | Grade 10.9 |
|---|---|---|---|
| Tensile Strength (Rm) min. | 420 MPa | 800 MPa ✅ | 1040 MPa |
| Proof Load (Sp) min. | 310 MPa | 600 MPa ✅ | 830 MPa |
| Yield Strength (Rp0.2) min. | 340 MPa | 640 MPa ✅ | 940 MPa |
| Elongation (A) min. | 14% | 12% | 9% |
| Hardness (HRC) | — | 22–32 ✅ | 32–39 |
| Typical Use | Light-duty general | Standard structural ✅ | High-load structural |
| Property | Grade 8.8 Value |
|---|---|
| Property Class | 8.8 (per ISO 898-1 / DIN EN ISO 898-1) |
| Tensile Strength (Rm) min. | 800 MPa (116,000 psi) |
| Proof Load Stress (Sp) min. | 600 MPa |
| Yield Strength (Rp0.2) min. | 640 MPa (80% of Rm) |
| Elongation (A) min. | 12% |
| Reduction of Area (Z) min. | 52% |
| Hardness min. | 22 HRC / 250 HV |
| Hardness max. | 32 HRC / 320 HV |
| Heat Treatment | Quenched & Tempered (Q&T) for d > M16; may be non-Q&T for smaller sizes |
| Property | 10B21 (Boron Steel) | 35K (Medium Carbon Steel) |
|---|---|---|
| GB/T Standard | GB/T 6478 (CHQ Boron Steel) | GB/T 699 (Medium Carbon Steel) |
| Carbon Content (C) | 0.18–0.23% | 0.32–0.39% |
| Boron (B) | 0.0005–0.003% (key alloying element) | None |
| Manganese (Mn) | 0.70–1.00% | 0.50–0.80% |
| Hardenability | Excellent (boron-enhanced) | Good |
| Cold Heading | Excellent | Good |
| Typical Use | Grade 8.8 bolts M6–M36 | Grade 8.8 bolts, general structural |
⚠️ Thread Note: Due to the thick zinc coating, HDG bolts require oversized nuts (also HDG) to accommodate the increased thread dimensions. Always use matching HDG nuts with HDG bolts. Standard (non-galvanised) nuts will not fit without modification.
All dimensions in millimeters (mm). Data per DIN 933 / ISO 4017 standard. Note: HDG coating adds 45–100 μm per surface — use HDG nuts with appropriate thread allowance.
| Thread (d) | Pitch (mm) | s — A/F (mm) | e — A/C (mm) | k — Head Height (mm) | d_w min (mm) | Length Range (mm) |
|---|---|---|---|---|---|---|
| M6 | 1.0 | 10 | 11.05 | 4.0 | 8.9 | 10 – 80 |
| M8 | 1.25 | 13 | 14.38 | 5.3 | 11.6 | 16 – 100 |
| M10 | 1.5 | 17 | 18.90 | 6.4 | 14.6 | 20 – 120 |
| M12 | 1.75 | 19 | 21.10 | 7.5 | 16.6 | 25 – 150 |
| M16 | 2.0 | 24 | 26.75 | 10.0 | 22.5 | 35 – 200 |
| M20 | 2.5 | 30 | 33.53 | 12.5 | 27.7 | 45 – 200 |
| M24 | 3.0 | 36 | 39.98 | 15.0 | 33.3 | 50 – 200 |
| M30 | 3.5 | 46 | 50.85 | 18.7 | 42.8 | 60 – 200 |
| M36 | 4.0 | 55 | 60.79 | 22.5 | 51.1 | 70 – 200 |
* Custom sizes and lengths available on request. Contact FULLERKREG for non-standard requirements.
Note: HDG bolts typically have higher friction coefficients than electroplated bolts due to the rougher zinc surface. Use lubrication (wax, oil, or zinc-compatible lubricant) and verify torque with a qualified engineer:
| Thread | Torque (N·m) — 75% Proof Load | Clamp Force (kN) |
|---|---|---|
| M6 | 8 | 10.5 |
| M8 | 20 | 20.5 |
| M10 | 40 | 33.0 |
| M12 | 70 | 48.0 |
| M16 | 170 | 87.0 |
| M20 | 335 | 136.0 |
| M24 | 580 | 195.0 |
| M30 | 1150 | 307.0 |
| M36 | 2000 | 445.0 |
* HDG bolts have higher friction than electroplated bolts (μ ≈ 0.17–0.20 vs. 0.12 for lubricated electroplated). Always verify torque with a qualified structural engineer. For slip-critical connections, refer to EN 1090 or AISC 360 friction-type bolt specifications.
| Standard | Region | Description |
|---|---|---|
| DIN 933 | Germany / Europe | Hexagon head bolts — full thread (metric) |
| ISO 4017 | International | Hexagon head screws — full thread |
| GB 5783 | China | Hexagon head bolts — full thread |
| ISO 898-1 | International | Mechanical properties — Grade 8.8 definition |
| ISO 10684 | International | Fasteners — hot dip galvanised coatings specification |
| ASTM A153 | USA | Zinc coating (hot dip) on iron and steel hardware |
| EN ISO 1461 | Europe | Hot dip galvanised coatings on fabricated iron and steel articles |
FULLERKREG DIN 933 Grade 8.8 Hot Dip Galvanised Full Thread Hex Bolts — actual product photos:
| [Product Photo 1] | [Product Photo 2] | [Product Photo 3] | [Product Photo 4] |
Q: What is hot dip galvanising and how does it differ from electroplated zinc?
A: Hot dip galvanising (HDG) involves immersing steel fasteners in molten zinc at ~450°C, forming a metallurgically bonded zinc-iron alloy coating 45–100 μm thick. Electroplated zinc deposits a thin (5–12 μm) zinc layer electrochemically. HDG provides 5–10× more zinc thickness, a metallurgical bond (not just adhesion), and self-healing cathodic protection — resulting in 20–50+ years of outdoor service life vs. 2–5 years for electroplated zinc.
Q: Why do HDG bolts need special nuts?
A: The thick zinc coating (45–100 μm per surface) significantly increases the effective thread diameter of HDG bolts. Standard nuts will not fit. HDG bolts must be used with matching HDG nuts that have been manufactured with an oversized thread allowance to accommodate the zinc coating. FULLERKREG supplies matching HDG nuts and washers.
Q: What is 10B21 steel and why is it used for Grade 8.8 bolts?
A: 10B21 is a boron-alloyed cold heading quality (CHQ) steel per GB/T 6478. The boron addition (0.0005–0.003%) dramatically improves hardenability — allowing the steel to through-harden to Grade 8.8 mechanical properties even in larger diameters, using less alloying than conventional carbon steels. This makes it the preferred material for cost-effective Grade 8.8 bolt production.
Q: Are HDG bolts suitable for structural applications per EN 1090?
A: Yes. HDG Grade 8.8 bolts per ISO 10684 are widely used in structural steel construction per EN 1090 (European execution standard for steel structures). For slip-critical (friction-type) connections, verify the friction coefficient of the HDG surface with your structural engineer, as HDG surfaces have different slip factors than other finishes.
Q: Can HDG bolts be used in contact with stainless steel or aluminium?
A: Galvanic corrosion may occur when HDG (zinc-coated) steel contacts dissimilar metals in the presence of an electrolyte. In contact with stainless steel, zinc will corrode preferentially (sacrificially) — this may be acceptable or unacceptable depending on the application. In contact with aluminium, the galvanic potential difference is smaller. Consult a corrosion engineer for mixed-metal joint design.
Q: What is the service life of HDG bolts outdoors?
A: Service life depends on the environment. In rural/suburban atmospheres, HDG bolts typically last 40–70+ years. In industrial or coastal atmospheres, service life is 20–40 years. In aggressive marine or chemical environments, additional protection (paint, sealant) may be required. ISO 14713 provides guidance on expected service life by environment.
Q: Can I get ISO 10684 coating inspection reports?
A: Yes. FULLERKREG provides ISO 10684 HDG coating thickness inspection reports and ISO 898-1 Grade 8.8 mechanical property certificates upon request for wholesale and construction project orders.
FULLERKREG — Precision Fasteners to ISO/DIN/GB Standards. All technical data is provided for reference. Always verify fastener selection, torque requirements, and galvanic compatibility with a qualified structural engineer for structural and safety-critical applications.
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