Overview
EN ISO 10683:2018 (ISO 10683:2018) specifies requirements for non‑electrolytically applied zinc flake coating systems for steel fasteners. It covers coatings:
- with or without hexavalent chromium (Cr(VI));
- with or without a top coat;
- with or without lubricant (integral or subsequently added).
The standard applies to bolts, screws, studs, nuts (ISO and non‑ISO threads) and non‑threaded fasteners (washers, pins, clips). It is not applicable to mechanically applied zinc coatings and does not set requirements for fastener weldability or paintability. Coatings conforming to EN ISO 10683 are especially used for high‑strength fasteners (≥ 1 000 MPa) to reduce the risk of internal hydrogen embrittlement (IHE). Design and assembly guidance is provided in Annex A.
Key topics and requirements
- Coating system definition: composition, curing, and the role of zinc + aluminium flakes to form a conductive, sacrificial layer.
- Corrosion protection testing: mandatory and optional tests including neutral salt spray (ISO 9227) and sulfur dioxide / Kesternich tests (ISO 6988) to assess cabinet corrosivity and performance.
- Dimensional and functional checks: coating thickness, gaugeability and assemblability (thread clearance and tolerances), with measurement methods referenced (e.g., ISO 1463 microscopic method).
- Mechanical and physical properties: appearance, ductility, adhesion/cohesion, sacrificial cathodic protection and behaviour at elevated temperatures.
- Torque / clamp‑force relationship: testing per ISO 16047 to ensure joint performance with coated fasteners.
- Hydrogen embrittlement avoidance: precautions and process controls to mitigate IHE for high‑strength steels.
- Chemical safety: procedures for hexavalent chromium determination when present.
- Testing applicability and lot control: mandatory lot tests, in‑process checks and purchaser‑specified tests; designation and ordering requirements are specified.
Applications and users
Practical applications include any industry requiring durable, corrosion‑resistant coated fasteners where electroplating is unsuitable or hydrogen embrittlement must be avoided - for example automotive, heavy equipment, construction and industrial machinery. Typical users:
- Fastener manufacturers and platers
- Coating system suppliers and applicators
- OEM design and assembly engineers
- Quality control and testing laboratories
- Procurement and specification writers
Related standards and references
EN ISO 10683 references and aligns with other standards for testing and thread gauging, such as:
For designers, Annex A offers practical guidance on design and assembly of coated fasteners. Use EN ISO 10683:2018 when specifying non‑electrolytically applied zinc flake coatings to ensure consistent corrosion protection, functional performance and conformity across supply chains.
