ISO 4404-1:2012

Overview

ISO 4404-1:2012 - published by ISO - specifies a laboratory test method to determine the corrosion resistance of fire‑resistant, water‑containing hydraulic fluids (categories HFA, HFB and HFC as classified in ISO 6743-4). The standard evaluates how these fluids influence common hydraulic metals and metal pairings used in hydraulic systems and installations, helping manufacturers, test laboratories and system designers assess compatibility and long‑term corrosion risk.

Key technical topics and requirements

• Scope and purpose: Corrosion testing for water‑containing fire‑resistant fluids (HFA, HFB, HFC). A similar approach for non‑aqueous HFD fluids is covered in ISO 4404-2.
• Test specimens: Standard test strips (100 × 20 × 1 mm, hole for suspension) of steel, copper, brass, zinc and aluminium (specifications given in Table 1).
• Preparation: Mechanical polishing (P120 → P400 → P600), solvent cleaning, desiccation and initial mass measurement to 1 mg.
• Test assembly: Single or paired strips suspended in 250 ml of homogenized test fluid in covered beakers; paired strips arranged 1 mm apart.
• Controlled conditions: Immersion at 35 °C ± 1 °C for 672 h ± 2 h (28 days).
• Observations and measurements:
  • Visual inspection of strips and fluid (rating tables provided for metal surface effects and fluid changes).
  • Final mass measurement after specified solvent cleaning sequence (varies by fluid type).
• Test water and concentrate handling: Guidance for preparing HFAE/HFAS emulsions or solutions from concentrates; selection of diluent water (Annex A) can affect results.
• Reporting: Visual ratings, mass change (+ or −) and test conditions; Annex D provides reporting table format.
• Notes: Precision of the method has not been established; safety precautions are required when handling test fluids and solvents.

Practical applications and users

• Who uses it:
  • Hydraulic fluid manufacturers (product qualification)
  • Independent test laboratories and QA/QC facilities
  • Hydraulic system designers and maintenance engineers
  • OEMs and specifiers evaluating fluid/metal compatibility
• Why it matters:
  • Select fluids that minimize corrosion of system components
  • Inform material choices (e.g., limit zinc contact with HFC fluids; aluminium considerations in specific sectors)
  • Support maintenance schedules and risk assessment for fire‑resistant hydraulic installations

Related standards

• ISO 4404-2 - Determination of corrosion resistance for non‑aqueous (HFD) fluids
• ISO 6743-4 - Classification of fire‑resistant hydraulic fluids (HFA, HFB, HFC, HFD)
• ISO 20783-1 - Emulsion stability for certain fire‑resistant fluids
• ISO 3696, ISO 3819 and others referenced for laboratory materials and water quality

Keywords: ISO 4404-1, fire-resistant hydraulic fluids, corrosion resistance testing, HFA HFB HFC, hydraulic systems, metal corrosion testing, ISO standard.