Overview
ISO 8179-1:2017 specifies an external zinc‑based protective coating system factory‑applied to ductile iron pipeline components (pipes, fittings and accessories) covered by ISO 2531, ISO 7186 and ISO 16631. The standard requires a metallic zinc‑based layer - either pure metallic zinc (99.99% purity), zinc‑aluminium alloys or other zinc alloys - followed by a finishing layer (bituminous paint or compatible synthetic resin). It sets performance, inspection and test requirements to ensure consistent corrosion protection of ductile iron pipeline components.
Key topics and technical requirements
- Coating materials: Pure metallic zinc (99.99 %), zinc‑aluminium or other zinc alloys, plus a compatible finishing layer (bituminous or synthetic resin).
- Surface condition: Substrate must be dry and free of rust, oil, grease and loose particles before coating.
- Method of application: Metallic zinc or zinc alloy is applied by thermal spray (molten metal projected as droplets). Manufacturer defines acceptable surface appearance and minor irregularities.
- Zinc‑based coating mass:
- Typical requirement: ≥ 200 g/m2 mean, local minimum 180 g/m2.
- Low‑corrosivity agreement: 130 g/m2 mean, local minimum 110 g/m2.
- Higher masses may be agreed for very corrosive soils.
- Finishing layer thickness: Mean dry film thickness ≥ 70 µm, local minimum 50 µm; upper limit ≤ 250 µm to avoid blistering.
- Damage limits and repairs:
- Minor handling damage acceptable if < 5 cm2 per m2 and max 5 mm in minor dimension.
- Repairs by metallic zinc spray or zinc‑rich paint (>85% zinc in dry film); paint repair mass must be at least 20% above nominal metallic coating mass.
- Test and inspection methods:
- Factory quality control using coated tokens (250×100 mm or 500×50 mm) to measure zinc mass by mass difference with a correction factor.
- Dry film thickness measured by micrometer, weighing method or suitable gauges (magnetic, wet‑film correlation) per ISO 2808.
- Annex A describes field verification techniques (e.g., gas evolution method) and precautions for finished products.
- Soil corrosivity guidance: Annex B provides field‑of‑use considerations for selection of coating mass vs. soil characteristics.
Applications and users
ISO 8179-1:2017 is used by:
- Manufacturers of ductile iron pipes, fittings and accessories for factory coating specification and quality control
- Pipeline design engineers and specifiers who set corrosion‑protection requirements
- Procurement teams and asset owners (water, wastewater, buried pipelines) selecting coated ductile iron components
- Inspectors and testing laboratories performing acceptance checks and field verification
Related standards
Keywords: ISO 8179-1:2017, ductile iron pipes, zinc-based coating, metallic zinc, finishing layer, coating mass, dry film thickness, thermal spray, zinc-rich paint, corrosion protection.
Open preview (PDF)Ductile iron pipes, fittings, accessories and their joints — External zinc-based coating — Part 1: Metallic zinc with finishing layer