Product Overview Hot-dip galvanized (HDG) hex head bolts are heavy-duty structural fasteners manufactured from medium carbon steel, heat-treated to Grade 8.8, and protected by a thick zinc-iron alloy coating applied through the hot-dip galvanizing process. Unlike electroplated zinc, the hot-dip coating forms a metallurgically bonded barrier that delivers 15–20+ years of outdoor service life, making these bolts the industry standard for solar mounting systems, transmission towers, and outdoor steel frameworks where long-term corrosion resistance is critical. Available in M10 and M16 as highlighted sizes, with a full range from M8 to M30 on request. Dacromet and other coating options are also available for specific project requirements. Key Specifications Parameter Specification Strength Grade 8.8 Material Medium carbon steel (C1035 / C1045) Standard DIN 933 / ISO 4017 / GB/T 5783 Thread Metric coarse (M), full thread Surface Finish Hot-dip galvanized (HDG) Zinc Coating Thickness 60 μm – 85 μm (customizable) Thread Diameter M8 – M30 (M10, M16 in stock) Length Range 10 mm – 300 mm (custom lengths available) Head Type Hexagon head Mechanical Properties (ISO 898-1 / GB/T 3098.1) Property Value Minimum Tensile Strength (Rm) 800 MPa Minimum Yield Strength (Rp0.2) 640 MPa Minimum Proof Load Stress (Sp) 580 MPa Core Hardness 22–32 HRC Elongation After Fracture (A min) 12% Material Condition Quenched and tempered These values correspond to the ISO 898-1 requirements for property class 8.8 fasteners. The bolts are heat-treated to meet or exceed 800 MPa tensile strength, providing the mechanical reliability required for structural steel connections. Coating Options: HDG vs. Dacromet Hot-Dip Galvanizing (HDG) is the standard finish for these bolts. The process involves dipping the finished bolt into molten zinc, creating a thick, abrasion-resistant zinc-iron alloy layer that is metallurgically bonded to the steel substrate. Key advantages include: Thick coating (60–85 μm) — significantly thicker than electroplated zinc, providing superior barrier protection Self-healing protection — if the coating is scratched, the surrounding zinc sacrificially protects the exposed steel Proven outdoor durability — 15–20+ years of service life in atmospheric exposure Dacromet is an alternative zinc-chromium-based coating that offers excellent corrosion resistance and stable weatherability without hydrogen embrittlement risk. It is particularly suitable for thin-walled rooftop solar brackets where electroplated fasteners are prohibited due to hydrogen embrittlement concerns. However, Dacromet may degrade under long-term UV exposure, making HDG the preferred choice for ground-mounted and transmission tower applications. Standards & Compliance These bolts conform to DIN 933 (fully threaded hexagon head screws), ISO 4017, and GB/T 5783. The hot-dip galvanizing process follows ASTM A153 and ISO 1461 standards for coating thickness and adhesion. For transmission tower applications, the bolts are also available to ASTM A394 Type 0 (hot-dip zinc-coated, low/medium carbon steel) or Type 1 (quenched and tempered) specifications. Applications Grade 8.8 HDG hex bolts are specified for demanding outdoor structural connections: Solar mounting systems — ground mounts, rooftop brackets, and tracker systems Transmission towers & substations — steel lattice tower connections, antenna mounts, and substation structures Heavy construction — steel warehouses, bridge components, and outdoor scaffolding Wind power infrastructure — tower section connections and foundation anchors Outdoor steel frameworks — exposed structural steel where long-term corrosion resistance is essential Available Sizes Thread (M) Common Length Range Hex Across-Flats (s) M8 16 – 80 mm 13 mm M10 20 – 100 mm 16 mm M12 25 – 150 mm 18 mm M16 30 – 200 mm 24 mm M20 40 – 300 mm 30 mm M24 60 – 300 mm 36 mm M30 80 – 300 mm 46 mm Full range available from M8 through M30, with lengths from 10 mm to 300 mm. M10 and M16 are held in ready stock for immediate shipment. Custom diameters, lengths, thread lengths, and washer combinations are available on request. Ordering Information Thread sizes: M8–M30 standard; M10, M16 in stock Lengths: 10–300 mm standard; custom lengths available Strength grades: 4.8, 8.8 standard; other grades on request Coatings: Hot-dip galvanized (standard); Dacromet available Fastener sets: Available as bolt only, or complete set with hex nut, flat washer, and spring washer Packaging: Bulk carton, export pallets, or customized packaging Documentation: Mill test certificates, salt spray test reports, and material traceability available Please inquire for specific size combinations, volume pricing, and lead times. Quality Assurance Each production batch is subject to mechanical property testing in accordance with ISO 898-1, including tensile strength, proof load, hardness, and elongation verification. Coating thickness is verified per ASTM A153 / ISO 1461. Third-party inspections (SGS, BV, TUV) are available upon request. Material certificates and test reports are available for every shipment.