ISO 9225:2012

Overview

ISO 9225:2012 - "Corrosion of metals and alloys - Corrosivity of atmospheres - Measurement of environmental parameters affecting corrosivity of atmospheres" - specifies standardized methods for measuring the environmental parameters used to estimate atmospheric corrosivity (the system used in ISO 9223). The standard defines how to measure the temperature–humidity complex and airborne contaminants (notably SO2 and airborne chlorides), plus specific deposition-measurement procedures and conversion factors in its normative annexes.

Key technical topics and requirements

• Scope and purpose
  • Measurement methods required for both normative (first-year corrosion rate calculations) and informative corrosivity estimations.
  • Emphasis on comparability and applicability of field methods to support ISO 9223 classification.
• Humidity and temperature
  • Yearly mean values are preferred to capture seasonal variation.
  • Recommended instruments: hygrographs, thermohygrographs, logging hygrometers/thermometers. Long-term meteorological data may be used where reliable.
• Airborne contaminants
  • Mandatory measurement of SO2 and chloride levels (either concentrations in µg/m³ or deposition rates in mg/(m·d)).
  • Acceptable techniques: continuous gas analyzers, active samplers (pumped), diffusive (passive) samplers, and deposition collectors.
  • Typical sampling durations:
    • Continuous monitoring: record monthly averages; express as yearly mean.
    • Active samplers: weekly sampling with aggregation to monthly/annual means.
    • Diffusive samplers: recommended 1 month (up to 3 months); annual aggregation recommended.
• Placement and installation
  • Instruments sheltered from rain; intake tubing (polyethylene or PTFE) ideally ≤ 2 m and inlet facing down; deposition equipment sheltered from washing and large particulates.
• Deposition measurement methods
  • Normative annexes define specific procedures:
    • Annex A/B/C: SO2 deposition on lead dioxide plates/cylinders and alkaline surfaces.
    • Annex D/E: Chloride deposition by wet candle and dry plate methods.
    • Annex F: Comparison/conversion factors between methods (important because methods produce different absolute deposition rates; e.g., wet candle vs dry plate).
• Safety note
  • Some procedures use potentially hazardous chemicals (e.g., lead compounds); follow applicable safety and local regulations.

Practical applications and users

• Who uses ISO 9225: corrosion engineers, materials scientists, environmental monitoring laboratories, infrastructure/asset owners (bridges, buildings, offshore structures), coatings and alloy manufacturers, and standards bodies.
• Typical uses:
  • Site characterization for corrosion risk assessment and material selection.
  • Input data collection for ISO 9223 corrosivity classification and lifetime/cost forecasting.
  • Setting monitoring programs for coastal, industrial or urban exposure sites.

Related standards

• ISO 9223 - Corrosivity classification and estimation (uses ISO 9225 measurement inputs).
• ISO 11844-3 - Measurement of environmental parameters for low-corrosivity indoor atmospheres.
• ISO 8565 - Site characterization methods (general exposure-site guidance).

Keywords: ISO 9225:2012, corrosivity of atmospheres, measurement of environmental parameters, SO2 deposition, chloride deposition, diffusive sampler, hygrograph, deposition rates, ISO 9223.