Overview
ISO 9350:2025 - Corrosion of metals and alloys - Testing method of corrosion resistance for hafnium at high temperature and pressure - defines a standardized laboratory method to evaluate hafnium corrosion in high-temperature, high-pressure water. The method specifies exposure at 360 °C and nominal 18.7 MPa for 672 hours, with corrosion assessed by mass gain and surface (oxide film) inspection. It applies to hot‑ or cold‑worked hafnium rods, wires, plates, sheets and strips and is intended for product acceptance testing as well as performance evaluation related to nuclear applications (e.g., pressurized water reactors).
Key topics and requirements
- Test principle: Controlled autoclave exposure of hafnium specimens in water; primary metrics are mass gain and visual surface appearance.
- Specimens: Individual identification, options for etched or as‑manufactured surfaces; guidance on coupon preparation (see Annex A).
- Test conditions: Temperature 360 °C, test pressure ~18.7 MPa, duration 672 h (document allows contractor‑specified pressure variations as required).
- Water quality: Grade A (≥ 1 MΩ·cm) or Grade B (≥ 0.5 MΩ·cm) purified/deionized water; only analytical‑grade reagents otherwise.
- Reagents & gases: Etching involves acids (HF, HNO3); argon gas of high purity (999.9 ml/l) is referenced.
- Apparatus: Autoclaves constructed from type 300 series stainless steel or specified nickel‑base alloys; equipment for precise measurement of mass (0.1 mg), dimensions (20 µm), temperature and pressure control.
- Calibration & control: Use of control coupons to validate test runs; procedures for autoclave cleaning, calibration and venting methods.
- Safety: Hazards from concentrated acids, high‑pressure/high‑temperature operations, and handling of hafnium products are highlighted; follow manufacturer and regulatory safety practices.
Applications and users
- Primary applications: Product acceptance testing, quality control, material development and performance prediction of hafnium used as a neutron absorber in nuclear reactors.
- Who uses it: Materials testing laboratories, nuclear component manufacturers, quality assurance engineers, R&D teams developing hafnium rods/plates/strips, and regulatory bodies overseeing nuclear materials.
- Practical value: Provides consistent, repeatable criteria for comparing hafnium corrosion resistance across suppliers and labs and for verifying conformity to purchaser requirements.
Related standards
- Prepared by ISO/TC 156 (Corrosion of metals and alloys). While ISO 9350:2025 contains no normative references, users commonly consult other ISO corrosion and materials test standards and national regulations for complementary procedures, safety and conformity assessment.
Keywords: ISO 9350:2025, hafnium corrosion test, high temperature high pressure, autoclave testing, mass gain measurement, control coupon, corrosion resistance, pressurized water reactor, specimen preparation.
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