Overview
ISO 19735:2023 - "Corrosion of metals and alloys - Corrosivity of atmospheres - Mapping areas of increased risk of corrosion" (First edition, 2023) provides guidance for producing corrosivity maps and related risk maps for outdoor, open atmospheres (excluding sheltered or semi‑sheltered positions). The standard requires maps to be calculated from environmental datasets using dose‑response functions (statistical relationships that estimate corrosion loss from environmental parameters). Other mapping approaches based on interpolated corrosion measurements are outside its scope.
Key topics and requirements
- Scope limitations
- Applies only to outdoor open atmospheres, not sheltered/semi‑sheltered locations.
- Maps must be based on environmental input data and dose‑response functions.
- Dose‑response functions
- For global mapping of carbon steel, zinc, copper and aluminium (categories C1–C5, CX), use the functions specified in ISO 9223; other functions may be used with clear disclosure.
- Functions must be derived from statistical analysis of field exposure data (ISO 8565) or explicitly documented if modified.
- Environmental data
- Use annual averages or longer time spans; clearly indicate the years used.
- Data must fall within the parameter ranges used to derive the dose‑response functions; mark any extrapolations.
- Transform all input datasets to a common grid system and resolution before applying dose‑response functions.
- Presentation
- Express uniform corrosion in micrometres (µm); localized corrosion averaged by g/m if needed.
- Map corrosivity using a colour scale (lighter = low, darker = high) tied to ISO 9223 categories.
- Lifetime and cost mapping
- Use time expressions in the dose‑response function or ISO 9224 relationships (D = r_corr · t^b) to map lifetimes and calculate replacement/maintenance cost per year.
- Error and uncertainty
- Dose‑response estimates carry substantial uncertainty (statistical error ~±50% per ISO 9223 Annex A) plus errors from environmental datasets, grid scale and temporal extrapolation. The standard recommends estimating and reporting these errors.
Practical applications and users
ISO 19735:2023 is useful for:
- Corrosion engineers and materials scientists producing regional or national corrosivity atlases
- Infrastructure and asset managers assessing geographic corrosion risk
- Urban planners and coastal engineers evaluating material selection and maintenance needs
- Environmental agencies and policy makers quantifying benefits of air‑quality measures (cost‑saving scenarios)
- Researchers modeling climate/pollution impacts on material degradation
Related standards
- ISO 9223:2012 - Corrosivity classification and dose‑response functions
- ISO 9224:2012 - Guiding values for corrosivity categories (time expressions)
- ISO 8565 - Field exposure procedures for deriving dose‑response data
Keywords: ISO 19735:2023, corrosivity maps, dose‑response functions, corrosion mapping, corrosivity of atmospheres, ISO 9223, ISO 9224, environmental data, lifetime mapping, corrosion cost, atmospheric corrosion.
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