Overview - ISO 14657:2005 (Zinc‑coated steel for the reinforcement of concrete)
ISO 14657:2005 specifies requirements for hot‑dip zinc (galvanized) coating on steel reinforcing bars, wire and welded fabric used in concrete reinforcement. It defines three coating classes (A, B, C) by minimum zinc mass per unit area, sets finish and adherence expectations, inspection and testing rules, repair limits for damaged coating, packing/labeling requirements, and purchaser information. The standard does not apply to hot‑dip zinc‑coated prestressing reinforcements.
Keywords: ISO 14657, zinc‑coated steel, galvanized reinforcement, hot‑dip galvanizing, concrete reinforcement
Key topics and technical requirements
- Coating classes and minimum zinc mass
- Class A: 600 g/m2 for diameter d > 6 mm; 500 g/m2 for d ≤ 6 mm
- Class B: 300 g/m2 for all diameters
- Class C: 140 g/m2 for all diameters
- Conversion to thickness: e (µm) = m (g/m2) / 7.14
- Finish & adherence
- Finish must meet ISO 1461 guidance; no sticking, dangerous spikes or tears.
- Adherence verified by bend/rebend or knife tests depending on production route.
- Mechanical and geometrical properties
- Reinforcement must still meet the applicable product standard (e.g., ISO 6935 series, ISO 10544) after galvanizing.
- Inspection & testing
- Test unit definitions: inspection by cast (40 t per unit) or batch (20 t per unit).
- Required tests per test unit: tensile, bend/rebend, geometry, weld shear (for fabric), and zinc mass (at least 3 samples).
- Coating mass measured per ISO 1460; thickness methods referenced (e.g., ISO 2178).
- Repair and damaged coating
- Damaged areas must be repaired with a zinc‑rich formulation.
- Max damaged (pre‑repair) surface ≤ 0.5% in any 1 m length.
- Minimum repaired coating thickness specified per class (see standard).
- Optional chromate treatment
- Chromate passivation options and guidance are included (Annex A) to reduce cement‑zinc reactions.
Practical applications
- Use ISO 14657 when specifying or procuring galvanized reinforcing bars, wire, or welded fabric for reinforced concrete elements where corrosion protection from zinc coating is required.
- Useful in coastal, industrial or aggressive environments where extra corrosion resistance is needed compared with uncoated steel.
- Applies to manufacturing, quality control, inspection, procurement and site acceptance preparations (note: site practice guidance is informative).
Who uses this standard
- Structural and civil engineers specifying reinforcement
- Steel manufacturers and galvanizers
- Construction contractors and fabricators
- Quality inspectors, testing laboratories and procurement/specification teams
Related standards
ISO 14657 helps ensure consistent, testable performance for zinc‑coated reinforcement, improving durability and traceability of galvanized steel used in concrete construction.