Overview
ISO 24131-2:2023 - Internal protection by polymeric lining for ductile iron pipes - Part 2: Epoxy lining defines requirements and test methods for factory‑applied internal epoxy linings on ductile iron pipes (per ISO 2531, ISO 7186 and ISO 16631). The standard covers epoxy linings used in the conveyance of raw water, potable water and sewage at operating temperatures up to 50 °C, and applies to both fusion‑bonded epoxy powder and two‑pack liquid epoxy systems.
Key technical topics and requirements
- Scope: Factory applied internal epoxy lining for ductile iron pipes for water and sewage applications (≤ 50 °C).
- Lining types: Fusion‑bonded epoxy powder and two‑pack liquid epoxy (resin + hardener).
- Surface preparation: Surfaces must be clean, oil‑ and moisture‑free; manufacturer must demonstrate fitness‑for‑purpose. Guidance references ISO 8501‑1 (Class Sa 2.5) and ISO 8502‑3 for dust criteria.
- Appearance: Uniform colour and smoothness; free of visible defects (pinholes, bubbles, blisters, cracks), with minor chalking or repair marks permitted.
- Minimum thickness: Local thickness > 200 µm; average thickness ≥ 250 µm (measured per 6.1.3).
- Adhesion: Pull‑off test (ISO 4624) or cross‑cut knife test (Annex B). Required adhesion: average ≥ 8.0 MPa, minimum single value ≥ 6.0 MPa.
- Cross‑linking: Assessed by MIBK test and ΔTg (ISO 11357‑2) to verify cure.
- Non‑porosity (holiday test): Electrical puncture testing to ensure absence of pinholes.
- Performance tests: Include abrasion and chemical resistance (for sewage), impact and indirect impact resistance, resistance to hot water, and resistance to ovalization.
- Quality assurance: Manufacturer quality control requirements are specified in Annex A; handling, transport and storage guidance in Annex C.
- Test classification: Routine production tests and performance tests (for material/process changes).
Applications and practical value
- Protecting ductile iron pipe interiors from corrosion and degradation in drinking water distribution, raw water transfer, and sewage systems.
- Ensuring safe contact materials for potable water by specifying adhesion, non‑porosity and chemical resistance.
- Providing procurement and specification criteria for pipe manufacturers, coating applicators, testing laboratories and utilities.
- Enabling consistent factory quality control and traceability for infrastructure projects.
Who should use this standard
- Ductile iron pipe manufacturers and coating processors
- Water and wastewater utilities and asset owners
- Engineering consultants, specifiers and procurement teams
- Third‑party test laboratories and conformity assessors
- Regulators and standards committees
Related standards
- ISO 2531 - Ductile iron pipes, fittings and joints for water applications
- ISO 7186 - Ductile iron products for sewerage applications
- ISO 16631 - Ductile iron pipes compatible with plastic piping systems
- ISO 4624 - Pull‑off test for adhesion
- ISO 11357‑2 - Differential scanning calorimetry (glass transition)
Keywords: ISO 24131-2:2023, epoxy lining, ductile iron pipes, internal protection, polymeric lining, test methods, lining thickness, adhesion, holiday test, potable water, sewage.