Overview
ISO 22479:2019 - Corrosion of metals and alloys - Sulfur dioxide test in a humid atmosphere (fixed gas method) - specifies a laboratory method to assess the resistance of materials and products to corrosion in a humid atmosphere containing sulfur dioxide (SO2). The standard applies to metals and alloys, metallic and non‑organic coatings, and organic coatings, using the fixed gas method (a fixed volume of SO2 introduced into a sealed test cabinet of fixed volume).
Key changes from prior versions include combining ISO 3231 and ISO 6988 and removing reagent-based generation of SO2 for safety.
Key topics and technical requirements
- Test principle: SO2 dissolved in moisture condenses on specimen surfaces and induces corrosion; the test reproduces this mechanism in a controlled cabinet.
- Test cabinet: Preferred capacity (300 ± 10) L; hermetically sealed, heated floor/lower walls, inclined lid (~12°) to prevent condensate drip, pressure relief valve, drain port, gas inlet positioned <50 mm above water surface.
- SO2 source & measurement: High‑purity SO2 gas cylinders (>99.9 %) with calibrated flowmeters or alternative volumetric methods (examples: 0.2, 1.0, 2.0 L gas volumes).
- Specimen preparation & dimensions: Typical specimen ~150 × 100 mm, thickness 0.75–1.25 mm; coatings prepared per ISO 1514 and thickness checked per ISO 2808. Clean and protect cut edges where applicable.
- Arrangement & clearances: Minimum spacing between specimens 20 mm; edge-to-cabinet-wall ≥100 mm; lowest edge >200 mm above water surface to avoid dripping or shielding.
- Conditioning: New cabinets require an initial conditioning cycle (e.g., 2.0 L SO2) to minimize cabinet material effects.
- Environmental control & safety: Room temperature recommendations (≈23 °C) and limited ambient humidity. WARNING: SO2 is toxic and corrosive - handling must be by skilled personnel; exhaust and relief gases must be treated per regulations.
Applications and who uses ISO 22479
- Corrosion testing laboratories performing standardized SO2 exposure tests.
- Coatings and surface treatment manufacturers validating resistance of paints, varnishes and metallic coatings.
- Materials and component manufacturers (automotive, marine, power generation, infrastructure) assessing metal/alloy durability in polluted/humid environments.
- Quality assurance, procurement and specification engineers referencing standardized test results for supplier acceptance and material selection.
- Research & development teams comparing corrosion behaviour of new alloys and protective systems.
Keywords: ISO 22479, sulfur dioxide test, humid atmosphere, fixed gas method, corrosion testing, metals and alloys, coatings.
Related standards
- ISO 1514 - Standard panels for testing (paints and varnishes)
- ISO 2808 - Determination of film thickness (paints and varnishes)
- ISO 8044 - Corrosion of metals and alloys - Basic terms and definitions
For safe and compliant implementation, follow the standard text for test cycles, durations, and reporting requirements, and observe local regulations for toxic gas handling and exhaust treatment.
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