Overview
ISO 4404-2:2010 - "Petroleum and related products - Determination of the corrosion resistance of fire-resistant hydraulic fluids - Part 2: Non‑aqueous fluids" - specifies a laboratory test procedure to assess the corrosion resistance and corrosion‑inhibiting properties of non‑aqueous, fire‑resistant hydraulic fluids (category HFD per ISO 6743‑4). The standard gives a reproducible qualitative and semi‑quantitative method for evaluating fluid compatibility with common hydraulic system metals.
Key topics and technical requirements
- Scope: Tests non‑aqueous fire‑resistant hydraulic fluids (HFD family). Water‑based fluids are covered in ISO 4404‑1.
- Test pieces: Standard metal specimens - steel, copper (electrolytic), brass, zinc, aluminium (dimensions and compositions specified). Other metals/alloys may be substituted for specific installations.
- Preparation: Polishing sequence using silicon‑carbide abrasives, solvent cleaning (heptane, toluene), and controlled handling to avoid cross‑contamination.
- Test conditions:
- Immersion of single and paired metal strips in (250 ±10) ml fluid per beaker.
- Temperature: (35 ±1) °C in a thermostatic bath/oven.
- Duration: (672 ±2) hours (28 days).
- Measurements and observations:
- Mass change recorded to nearest 0.5 mg (balance precision 0.2 mg).
- Visual classification scales for test‑piece corrosion (0–5) and test‑fluid condition (0–5).
- Paired tests examine galvanic or mutual effects (steel/zinc, copper/zinc, aluminium/zinc, steel/aluminium).
- Apparatus/consumables: Borosilicate beakers, watch‑glasses with closures, glass hooks, nylon spacers/bolts, abrasive cloths, heptane and toluene.
- Reporting: Full test report including product ID, mass changes, corrosion classifications, any deviations, and date.
Note: ISO 4404‑2 includes a safety warning - use involves hazardous materials and appropriate safety controls are required.
Applications and users
ISO 4404‑2 is used for:
- Product development and formulation screening of fire‑resistant hydraulic fluids.
- Quality control and batch verification by fluid manufacturers and independent test laboratories.
- Hydraulic system designers, specifiers, and maintenance engineers assessing material compatibility and corrosion risk in industrial and mobile hydraulic systems.
- Procurement and compliance checks where corrosion resistance of HFD fluids is a selection criterion.
Keywords: ISO 4404‑2, corrosion resistance test, fire‑resistant hydraulic fluids, HFD fluids, hydraulic system compatibility, non‑aqueous fluids.
Related standards
- ISO 4404‑1 - Determination of corrosion resistance for water‑containing fluids (HFA/HFB/HFC).
- ISO 6743‑4 - Classification of hydraulic fluids (Family H).
- Normative references used in procedure: ISO 3170, ISO 3819, ISO 5272.
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