Overview
ISO 22426:2020 - Assessment of the effectiveness of cathodic protection based on coupon measurements - defines requirements for using coupons (metal samples or probes) to assess cathodic protection (CP) effectiveness for buried and immersed metallic structures such as pipelines. The standard covers the design, installation, positioning, sizing, use and maintenance of coupons for normal operation and under AC and DC interference conditions. It addresses situations where direct IR-free potential or instant-off measurements on the structure are impractical or impossible and where coupons provide the practical alternative to demonstrate CP performance.
Key topics and requirements
- Scope and terminology: Definitions for coupon, probe, IR-free potential, instant-off, on-potential, spread resistance, polarization and related terms.
- Measurement principles: Guidance on IR-free potential vs. instant-off vs. on-potential measurements, and the limitations of direct structure measurements on modern coated assets.
- AC / DC interference: Procedures and measurement requirements to assess CP effectiveness when AC interference or DC stray currents prevent conventional potential measurements.
- Coupon design and geometry: Requirements for coupon material equivalence, surface area, base plate dimensions and alternate geometries to represent coating defects reliably.
- Electrical and electrochemical parameters: Considerations for current and current density, spread resistance, and corrosion rate measurements on coupons.
- Installation, commissioning and monitoring: Site selection criteria, installation procedures, commissioning checks, measurement frequency and documentation practices to ensure representative and repeatable results.
- Annexes: Informative annexes covering special coupon/probe types (including ER probes), assessments under combined interference conditions, and examples of instant-off and current density measurements including remote monitoring.
Practical applications and users
ISO 22426:2020 is intended for:
- Pipeline and buried-structure owners and operators
- Corrosion engineers and CP designers
- Inspection, monitoring and maintenance teams
- Contractors installing CP test stations and coupons
- Regulatory and compliance personnel demonstrating conformity with CP performance criteria
Practical uses:
- Demonstrating CP effectiveness where direct IR-free potential measurements are unreliable (high-quality coatings, complex structures, multiple CP sources, stray currents)
- Measuring current density on coupons to assess AC corrosion risk
- Supporting compliance with pipeline CP standards and improving decision-making for maintenance and repair
Related standards
- ISO 15589-1 (Cathodic protection of pipeline systems - on-land pipelines)
- ISO 18086 (use of coupons and probes)
- EN 13509 (intensive measurement methods)
- EN 50162 (protection against stray current from DC systems)
For implementation or to obtain the full text, consult ISO or your national standards body. Keywords: ISO 22426:2020, cathodic protection, coupon measurements, CP effectiveness, pipeline corrosion, AC interference, DC interference, IR-free potential.
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