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FULLERKREG DIN 125A 140HV Hot Dip Galvanised flat washers are manufactured from carbon steel Q235 (mild steel, equivalent to S235 / A36) with a hot dip galvanised (HDG) zinc coating per ISO 10684. Conforming to DIN 125A, ISO 7089, and GB/T 97.1, these washers provide the highest level of corrosion protection available for carbon steel flat washers — with a zinc coating thickness of 45–85 μm (typically 10× thicker than electroplated zinc), delivering 20–50+ years of corrosion protection in outdoor structural and civil engineering applications.
Hot dip galvanising immerses the finished washer in molten zinc at approximately 450°C, forming a metallurgically bonded zinc-iron alloy layer that provides both barrier protection and cathodic (sacrificial) protection. Even if the coating is scratched or damaged, the surrounding zinc sacrificially protects the exposed steel. HDG is the preferred surface finish for long-term outdoor structural fastening in construction, infrastructure, and civil engineering.
Note: Due to the thick HDG coating (45–85 μm per side), HDG washers have slightly larger effective inner and outer dimensions than the nominal DIN 125A values. Verify clearance fit with mating bolt and nut before assembly. HDG nuts (oversize tapped) should be used with HDG bolts and washers.
| Standard | DIN 125A ≡ ISO 7089 ≡ GB/T 97.1 (dimensions) | ISO 10684 (HDG coating) |
| Type | Plain flat washer — normal series (Form A), chamfer on one side of inner hole |
| Material | Carbon Steel Q235 (S235 / A36 / mild steel) |
| Heat Treatment | None — as-stamped (cold formed) |
| Hardness | ~140 HV (typical for Q235 mild steel; ≤ 200 HV per ISO 7089 normal grade) |
| Surface Finish | Hot Dip Galvanised (HDG) — per ISO 10684 |
| Zinc Coating Thickness | 45 – 85 μm (per ISO 10684) |
| Salt Spray Resistance | ≥ 1000 hours to red rust (typical for 45–85 μm HDG) |
| Outdoor Service Life | 20 – 50+ years (environment-dependent, per ISO 14713) |
| Size Range | M6 – M36 |
| Recommended Bolt Grade | Grade 4.6, 4.8, 5.6, 6.8 (low to medium strength bolts); HDG bolts (DIN 931 / DIN 933 HDG) |
| Corrosion Resistance | Excellent — best-in-class for carbon steel; suitable for long-term outdoor, structural, and civil engineering use |
| Magnetic | Yes |
| Related Standard | ISO 10684 (HDG fasteners) | ISO 14713 (zinc coating durability) | ISO 7089 | GB/T 97.1 |
| [Product Photo 1] | [Product Photo 2] | [Product Photo 3] | [Product Photo 4] |
All dimensions in millimeters (mm). Nominal dimensions per DIN 125A / ISO 7089 standard (pre-coating). HDG coating (45–85 μm per surface) adds approximately 0.09–0.17 mm to each radius — verify clearance fit before assembly.
| Nominal Size (Bolt d) | d1 — Inner Ø (mm) | d2 — Outer Ø (mm) | h — Thickness (mm) | Weight (kg / 1000 pcs) |
|---|---|---|---|---|
| M6 | 6.4 | 12 | 1.6 | 0.68 |
| M8 | 8.4 | 16 | 1.6 | 1.21 |
| M10 | 10.5 | 20 | 2.0 | 2.37 |
| M12 | 13.0 | 24 | 2.5 | 4.73 |
| M14 | 15.0 | 28 | 2.5 | 6.43 |
| M16 | 17.0 | 30 | 3.0 | 8.98 |
| M18 | 19.0 | 34 | 3.0 | 11.8 |
| M20 | 21.0 | 37 | 3.0 | 14.2 |
| M22 | 23.0 | 39 | 3.0 | 15.6 |
| M24 | 25.0 | 44 | 4.0 | 27.4 |
| M27 | 28.0 | 50 | 4.0 | 35.9 |
| M30 | 31.0 | 56 | 4.0 | 45.4 |
| M33 | 34.0 | 60 | 5.0 | 64.3 |
| M36 | 37.0 | 66 | 5.0 | 83.2 |
* Nominal dimensions per DIN 125A / ISO 7089 (pre-coating). HDG coating adds ~0.09–0.17 mm per radius. Weights are approximate based on carbon steel density (7.85 g/cm³) excluding zinc coating weight. HDG starts from M6 due to coating thickness constraints on smaller sizes.
| Property | HDG (This Product) | Zinc CR3 | Black Oxide |
|---|---|---|---|
| Process | Hot dip in molten zinc (~450°C) | Electroplated zinc + CR3 passivation | Alkaline blackening |
| Zinc coating thickness | 45 – 85 μm | 5 – 8 μm | 1 – 2 μm (no zinc) |
| Coating type | Metallurgically bonded Zn-Fe alloy | Electrodeposited zinc | Iron oxide conversion |
| Salt spray resistance | ≥ 1000 hours | ≥ 240 hours | ≤ 24 hours |
| Outdoor service life | 20 – 50+ years | 3 – 10 years | Indoor only |
| Cathodic protection | Yes — sacrificial zinc | Yes — sacrificial zinc | No |
| Coating standard | ISO 10684 | ISO 4042 | — |
| Dimensional impact | Significant (+0.09–0.17mm/radius) | Minimal (+0.005–0.008mm) | Negligible |
| Appearance | Matte grey / spangled | Bright silver / blue iridescent | Matte black |
| Best for | Long-term outdoor structural, civil engineering | General outdoor, automotive | Indoor precision machinery |
| Property | Value |
|---|---|
| Base Material | Carbon Steel Q235 (S235 / A36 / mild steel) |
| Carbon Content | ≤ 0.22% (low carbon, mild steel) |
| Yield Strength | ≥ 235 MPa |
| Tensile Strength | 370 – 500 MPa |
| Hardness | ~140 HV (typical; ≤ 200 HV per ISO 7089 normal grade) |
| Surface Finish | Hot Dip Galvanised (HDG) per ISO 10684 |
| Zinc Coating Thickness | 45 – 85 μm (per ISO 10684) |
| Zinc Purity | ≥ 98.5% Zn (molten zinc bath) |
| Coating Bond | Metallurgical Zn-Fe alloy bond — cannot be peeled or chipped |
| Salt Spray Resistance | ≥ 1000 hours to red rust (typical) |
| Outdoor Service Life | 20–50+ years (per ISO 14713, environment-dependent) |
| Temperature Limit | Up to +200°C (HDG service limit before zinc oxidation accelerates) |
| Magnetic | Yes |
| Density (steel) | 7.85 g/cm³ |
Q: What is hot dip galvanising (HDG) and how does it differ from electroplated zinc?
A: Hot dip galvanising (HDG) immerses the steel part in a bath of molten zinc at approximately 450°C. The zinc reacts with the steel surface to form a series of zinc-iron alloy layers, topped by a pure zinc outer layer — creating a metallurgically bonded coating that cannot be peeled or chipped. The resulting coating is 45–85 μm thick — approximately 10× thicker than electroplated zinc (5–8 μm). HDG provides both barrier protection and cathodic (sacrificial) protection: even if the coating is scratched, the surrounding zinc sacrificially corrodes to protect the exposed steel.
Q: Why does HDG start from M6 rather than M3?
A: The thick HDG coating (45–85 μm per surface) significantly reduces the inner diameter clearance of small washers. For M3–M5 washers, the coating thickness relative to the inner diameter is too large to maintain reliable clearance fit with the bolt shank after galvanising. HDG is therefore practical from M6 upwards for DIN 125A washers. For M3–M5 sizes, specify Zinc CR3 electroplated washers.
Q: Do I need to use HDG nuts with HDG washers and bolts?
A: Yes. HDG bolts are supplied with oversize-tapped nuts to accommodate the zinc coating on the bolt threads. Standard nuts will not fit HDG bolts. Similarly, HDG washers have slightly larger effective dimensions due to the coating. For a complete HDG fastener assembly, specify HDG bolts, HDG oversize nuts, and HDG washers together.
Q: How long will HDG washers last outdoors?
A: Per ISO 14713, the service life of HDG zinc coatings depends on the corrosivity category of the environment. In a C2 (low corrosivity, rural) environment, 45–85 μm HDG provides 50+ years of protection. In a C3 (medium, urban/industrial) environment, 20–50 years. In a C4 (high, industrial/coastal) environment, 10–20 years. Contact FULLERKREG for specific service life estimates for your application environment.
Q: Can I use HDG washers with Grade 8.8 or 10.9 bolts?
A: HDG washers are 140HV soft washers suitable for Grade 4.6–6.8 bolts. For Grade 8.8, 10.9, or 12.9 high-tensile bolts, 300HV hardened washers are required to prevent embedding and preload loss. Note that HDG 300HV hardened washers are also available — contact FULLERKREG for availability.
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