Overview
ISO 17224:2015 specifies a laboratory test method for evaluating high‑temperature corrosion of metallic materials exposed to a corrosive deposit (salt, ash or other substances). The method covers preparation of test pieces, application of a deposit (by spraying, dipping or painting), exposure at elevated temperature in a controlled gas environment, and post‑test evaluation to determine corrosion resistance. It excludes tests where specimens are embedded in powders or immersed in liquids (see ISO 17248 and ISO 17245).
Key topics and technical requirements
- Test principle: Apply a defined deposit to metallic specimens and expose them to high temperature under a controlled gas flow; assess mass change, dimensional change and microstructure.
- Test pieces: Rectangular, disc or cylindrical specimens with a minimum surface area (document: 300 mm²) and minimum thickness 1.5 mm; final surface finish using abrasives (~15 µm mean particle diameter) and lightly rounded edges to avoid anomalies.
- Corrosive deposit: Prepared from actual ash or reagent‑grade chemicals; melting point should be known. Application methods: solution spray, suspension (dipping/painting) or dry powder. Typical deposit loads range from about 1 mg/cm² (sprayed salts) to ~30 mg/cm² (suspended ash), with drying before exposure recommended.
- Apparatus and atmosphere: Heating device with a testing chamber isolating specimens from ambient air; gas composition and flow controlled. Horizontal closed‑furnace design illustrated; test chamber materials must not significantly react with deposit or gas.
- Temperature control & monitoring: Furnace isothermal zone characterized with movable thermocouple. Permissible temperature tolerances (examples from the standard): ≤300 °C ±2 °C; 300–600 °C ±3 °C; 600–800 °C ±4 °C; 800–1 000 °C ±5 °C; 1 000–1 200 °C ±7 °C.
- Measurements and evaluation: Pre‑ and post‑test mass (precision ±0.05 mg between repeats), descaling protocols to remove corrosion products, surface and cross‑section metallography, and reporting of test material, environment and results. Annex A provides chemical/electrolytic removal procedures.
Practical applications and users
ISO 17224:2015 is used to:
- Compare corrosion resistance of alloys and coatings in environments where salts or ashes contact hot surfaces.
- Evaluate material performance for boilers, furnaces, heat‑exchangers, gas‑turbine and combustion systems where deposits form.
- Support materials selection, failure analysis, QA of high‑temperature components, and R&D for corrosion‑resistant alloys.
Typical users: materials and corrosion engineers, metallurgists, test laboratories, OEMs in power generation, petrochemical and waste‑to‑energy industries, and academic researchers.
Related standards
- ISO 17248 - compacted powder deposit testing
- ISO 17245 - immersion in molten liquids
- ISO 21608 - isothermal high‑temperature oxidation testing
- ISO 8044, ISO 8407 and other normative references cited for terminology, descaling and measurement methods
Keywords: ISO 17224:2015, high temperature corrosion testing, corrosive deposit, salt ash deposit, metallic materials, controlled gas environment, corrosion resistance, test method.
Open preview (PDF)Corrosion of metals and alloys — Test method for high temperature corrosion testing of metallic materials by application of a deposit of salt, ash, or other substances
