Overview
EN ISO 9224:2012 - Corrosion of metals and alloys: Corrosivity of atmospheres - Guiding values for the corrosivity categories (ISO 9224:2012) - provides standardized, engineering‑useful guiding values for atmospheric corrosion of common metals and alloys for outdoor exposures greater than one year. Published by CEN as EN ISO 9224:2012 (identical to ISO 9224:2012), the document is intended to be used in conjunction with ISO 9223 to interpret corrosivity categories in quantitative terms for material selection, life prediction and protective design.
Key topics and requirements
- Guiding corrosion values: Defines corrosion rates, mass loss or penetration characteristics that represent the expected corrosive action for each standardized corrosivity category.
- Prediction method: Presents the mathematical principle and time‑exponent approach to predict corrosion attack after extended exposures using first‑year corrosion data and appropriate time exponents.
- Material‑specific criteria: Gives calculation procedures and guidance for standard structural materials, including steels, zinc, copper alloys and aluminium alloys. Annex C specifically addresses the effect of steel composition on long‑term corrosion.
- Examples and data: Annex A provides example calculations of maximum corrosion attack for exposures up to 20 years; Annex B supplies average initial and steady‑state corrosion‑rate intervals relative to the six corrosivity categories.
- Conservative estimates: Explains how to obtain upper‑limit (conservative) estimates of corrosion attack and warns about the limitations of long‑term extrapolation beyond documented exposure ranges.
- Scope limitations: Does not address localized degradation mechanisms in detail (e.g., pitting, crevice corrosion, galvanic corrosion, environmental cracking, or corrosion product wedging).
Practical applications
- Use EN ISO 9224:2012 for engineering calculations to estimate metal loss or penetration over service lives and to determine whether protective measures (coatings, material upgrades) are required.
- Support material selection for outdoor structures, civil infrastructure, industrial plants and transport equipment exposed to atmospheric environments.
- Inform life‑cycle cost and maintenance planning, helping asset managers predict replacement intervals and schedule inspections.
- Provide input for protective system design and specification (e.g., coating thickness, sacrificial anodes) and for compliance with national standards where EN ISO 9224 is adopted.
Who will use this standard
- Corrosion and materials engineers, structural engineers, specifiers, coating manufacturers, asset managers, and standards bodies involved in outdoor atmospheric exposure assessments.
Related standards
- ISO 9223 - Corrosivity of atmospheres: Classification, determination and estimation (to be used together)
- ISO 8044 - Basic terms and definitions for corrosion of metals
- ISO 11303 - Guidance for selection of protection methods against atmospheric corrosion
Note: EN ISO 9224:2012 provides globally referenced, evidence‑based guidance for long‑term atmospheric corrosion assessment but users should consult specialists for cases dominated by localized corrosion mechanisms or rapidly changing environments.
