Overview
ISO 9658:1990 specifies a flame atomic absorption spectrometric (FAAS) method for the determination of aluminium in steels, covering both acid-soluble and total aluminium in the range 0.005 % (m/m) to 0.20 % (m/m). The standard defines the principle, reagents, apparatus, sampling, detailed procedures, calculation and expression of results, reporting requirements and annexed instrumental and precision criteria based on international inter‑laboratory trials.
Key topics & technical requirements
- Scope & range: Applicable for acid-soluble and/or total Al between 0.005–0.20 % (m/m). Alternative preparation steps and calibration tables are given for the 0.010–0.20 % range.
- Sample preparation
- Acid-soluble Al: add fusion mixture solution, cool, vent CO2, dilute to volume, discard insoluble residue (retain filtrate).
- Total Al: char and ignite insoluble residue, treat with HF and H2SO4, fuse, dissolve fusion products in HCl and water, transfer to volumetric flask.
- Calibration & matrix matching: Calibration solutions are prepared using an iron matrix and aluminium standard additions (tables supplied). A fresh calibration graph is required for each series of determinations.
- Instrumental settings (FAAS)
- Lamp: aluminium hollow-cathode; wavelength 309.3 nm.
- Flame: dinitrogen monoxide–acetylene, non‑luminous oxidizing flame; red-feather height 10–20 mm.
- Bandwidth: follow manufacturer; if unspecified, 0.2–0.7 nm suggested.
- Background correction may be necessary if zero member shows measurable absorbance.
- Performance & quality criteria
- Procedures for limit of detection, characteristic concentration, minimum precision and graph linearity (e.g., AA/A1 ≥ 0.7) are detailed in Annex A.
- Precision (repeatability and reproducibility) was evaluated by 28 laboratories; results and logarithmic relationships are reported (Annex C).
- Safety & good practice: Warnings about acetylene hazards, UV protection, burner maintenance, water traps and frequent spraying of distilled water between solutions.
Applications & users
ISO 9658 is used for:
- Quality control and composition verification in steel production.
- Certification testing and compliance with material specifications.
- Metallurgical laboratories, third‑party testing bodies, failure analysis and R&D where accurate aluminium quantification in steel is required.
- Instrument manufacturers and laboratory managers establishing FAAS methods and performance checks.
Related standards
- ISO 5725 (statistical methods for repeatability and reproducibility) is referenced for precision evaluation.
- Applicable FAAS instrument manufacturer guidance should be followed for lamp current, bandwidth and background correction settings.
Keywords: ISO 9658, aluminium determination, steel, flame atomic absorption spectrometry, FAAS, acid‑soluble aluminium, total aluminium, calibration, precision, metallurgical testing.
Open preview (PDF)Steel — Determination of aluminium content — Flame atomic absorption spectrometric method
