Overview
EN ISO 10684:2004 - Fasteners: Hot dip galvanized coatings specifies material, process, dimensional and selected performance requirements for spun hot dip galvanizing of coarse‑threaded steel fasteners. It applies to fasteners from M8 to M64, for property classes up to 10.9 (bolts, screws, studs) and 12 (nuts). The standard notes that galvanizing is not recommended for threaded fasteners smaller than M8 or with pitches below 1.25 mm. It may also be applied to other threaded parts and non‑threaded items such as washers.
Key topics and technical requirements
- Scope and applicability: Focus on spun hot dip galvanizing of threaded steel fasteners (M8–M64); guidance for washers and other parts.
- Materials: Requirements for base steel chemistry; caution where phosphorus + silicon content is 0.03–0.13 % (recommendation for high‑temperature galvanizing).
- Galvanizing process steps: Stress relief, cleaning/pickling (use of inhibited acids to limit hydrogen absorption), baking (to reduce hydrogen embrittlement risk), fluxing, immersion in molten zinc, immediate spinning and quenching.
- Bath temperatures: Normal galvanizing at 455–480 °C; high‑temperature galvanizing at 530–560 °C (duller, smoother finish). Galvanizing is not to be conducted between 480–530 °C.
- Thread and fit considerations: Thread tolerances and precautions for assembling hot dip galvanized threaded fasteners; special provisions for M8 and M10 (annexes).
- Coating requirements: Appearance, adhesion, measurement of zinc coating (reference to ISO 1460, ISO 1461, ISO 2178); batch and lot definitions for uniformity and testing.
- Mechanical effects: Notes on reduced proof/ultimate loads for undersized/oversized threads (see Annex A and informative annexes on strength calculations).
- Additional topics: Lubrication, post‑treatment, ordering/designation and marking, special nut requirements and sealed‑container marking.
Applications and users
- Who uses it: Fastener manufacturers, galvanizing processors, quality managers, procurement/specification engineers, structural and mechanical designers specifying corrosion protection for bolted connections.
- Practical uses:
- Specifying corrosion‑resistant coatings for structural and infrastructure fasteners.
- Defining manufacturing and inspection criteria for spun hot dip galvanized bolts, nuts, screws and washers.
- Informing design choices where galvanizing affects thread fit, mechanical properties or assembly (e.g., selection of undersize/oversize threads and lubrication).
Related standards
EN ISO 10684:2004 is essential when specifying hot dip galvanized coatings, ensuring consistent quality, safe mechanical performance and predictable assembly behavior of threaded fasteners.
