Overview - ISO 15906:2007 (air permeability of baked anodes)
ISO 15906:2007 specifies a laboratory method to measure the air permeability of baked carbonaceous anodes used in aluminium production. The standard defines a comparative test that determines the resistance to airflow through a cylindrical specimen at room temperature, covering a permeability range from 0.01 nPm to 10 nPm (nanoperms). “Green” (unbaked) anodes are treated as gas-impermeable; the method is intended primarily for baked anodes and similar carbon materials.
Key topics and technical requirements
- Test principle: comparative timing method - measure the time to draw a specified air volume through the specimen and compare with a calibrated standard to calculate permeability in nPm.
- Specimen geometry and preparation: 50 mm diameter (±0.4 mm), 20 mm height (faces parallel within ±0.05 mm). Cores are sampled per ISO 8007-2; outer 20 mm discarded, then a 20 mm section dried at 110 °C for 4 h.
- Apparatus essentials: permeability cell with airtight rubber seal, membrane vacuum pump (down to 100 mbar vacuum; outlet up to 4 bar; flow up to 25 L/min), U-tube manometer with proximity sensors, high‑precision capillary standards (1–2 nPm range) for calibration, and an impermeable disc for leak checks.
- Calibration and calculation: apparatus calibrated using capillary standards of known air permeability; test times between manometer sensor levels are used to compute a calibration factor and sample permeability (expressed in nPm).
- Precision: stated for anode samples in the 0.7–3.4 nPm range. Repeatability r = 0.06 nPm; reproducibility R = 0.04·X + 0.09 nPm (X = material average).
- Reporting: test report must reference the standard and include producer/customer names, batch references, test date/place, and results.
Applications and users
ISO 15906:2007 is practical for:
- Anode manufacturers performing quality control on baked anodes.
- Primary aluminium producers monitoring anode integrity to reduce air/CO2 attack and optimize anode life.
- Materials testing and QA/QC laboratories evaluating permeability for product acceptance or R&D.
- R&D groups developing microporous/carbonaceous materials where gas permeability is a performance parameter.
Measuring air permeability helps predict anode durability in reduction cells and supports process and material improvements.
Related standards
- ISO 8007-2:1999 - referenced for sampling plans and sampling from prebaked anodes.
- Prepared by ISO/TC 226 (Materials for the production of primary aluminium).
Keywords: ISO 15906:2007, air permeability, baked anodes, carbonaceous materials, aluminium production, nanoperms, anode testing, permeability measurement.