Overview
EN ISO 9225:2012 - "Corrosion of metals and alloys - Corrosivity of atmospheres - Measurement of environmental parameters affecting corrosivity of atmospheres" (ISO 9225:2012) defines standardized methods to measure the environmental parameters used to estimate atmospheric corrosivity (as classified in ISO 9223). The standard supports both normative corrosivity estimation (based on calculated first‑year corrosion rates of standard metals) and informative estimation (characterization of exposure environments). It does not prescribe laboratory analytical techniques but provides specific measurement procedures and conversion factors for key deposition methods.
Key topics and technical requirements
- Parameters covered
- Temperature and humidity (the temperature–humidity complex is a primary driver of atmospheric corrosion).
- Airborne contaminants, with mandatory focus on sulfur dioxide (SO2) and airborne chlorides (Cl−); other pollutants (NOx, O3, H2S, particulate deposits) are considered accompanying factors for informative estimation.
- Measurement methods
- Continuous gas concentration instruments.
- Active samplers (pumped sampling with absorption media).
- Diffusive (passive) samplers.
- Deposition-rate equipment (for measuring mass deposit on surfaces).
- Measurement practice
- Preferred measurement period: one year to capture seasonal variation; results reported as yearly mean values.
- Units: gas concentrations typically in µg/m3; deposition rates in mg/(m2·d).
- Placement guidance: instruments should be sheltered from rain and unauthorized access; tubing recommendations and orientation guidance are provided to minimize artefacts.
- Annexed procedures
- Annex A–C: SO2 deposition methods (lead dioxide sulfation plates/cylinders and alkaline surfaces).
- Annex D–E: Chloride deposition methods (wet candle and dry plate).
- Annex F: Comparison and conversion factors between different measurement methods.
Applications and who uses this standard
- Corrosion engineers and materials scientists use EN ISO 9225:2012 to collect standardized environmental data for corrosion rate estimation and selection of corrosion-resistant materials.
- Environmental monitoring laboratories implement the defined sampling and deposition procedures to produce comparable pollutant and deposition data.
- Asset owners / infrastructure managers apply results to inform maintenance scheduling, protective coatings selection, and service-life prediction for structures exposed to atmospheric environments.
- Coatings manufacturers and specifiers reference corrosivity classifications (ISO 9223) derived from EN ISO 9225 measurements to develop and validate protective systems.
- Standards bodies and regulators rely on the standard for consistent methods in corrosivity classification and reporting.
Related standards
- ISO 9223 - Corrosivity of atmospheres: classification and estimation (uses data produced according to EN ISO 9225).
- ISO 11844‑3 - Measurement of parameters affecting low indoor corrosivity (complements indoor-specific methods).
Keywords: EN ISO 9225:2012, corrosivity of atmospheres, measurement of environmental parameters, SO2 deposition, chloride deposition, humidity, temperature, corrosion estimation, ISO 9223.
