ISO 10138:1991

Overview - ISO 10138:1991 (Steel and iron - Chromium by FAAS)

ISO 10138:1991 specifies a flame atomic absorption spectrometric (FAAS) method for the determination of chromium content in non‑alloy and low‑alloy steels and iron. The method is applicable for chromium levels from 0.002 % (m/m) to 2.0 % (m/m). Publication of ISO 10138:1991 cancelled ISO 4936:1984. Annex A is integral (instrument performance), while Annexes B and C provide informational cooperative test data and graphical precision data.

Key topics and technical requirements

• Scope & applicability: Suitable for non‑alloy and low‑alloy steels and iron, Cr range 0.002–2.0 % (m/m).
• Sample preparation: Acid dissolution (hydrochloric acid), oxidation (nitric acid), filtration/ignition of insoluble residue, removal of silica with hydrofluoric acid, fusion of residue with potassium hydrogen sulfate (KHSO4) and acid extraction; combine extracts for analysis.
• Instrumentation: FAAS with a chromium hollow cathode lamp, dinitrogen monoxide–acetylene flame, and readout/recorder. Wavelengths used: 357.9 nm or 425.4 nm (choice depends on Cr level).
• Calibration & standards: Requires prepared chromium standard solutions (stock and working standards), background solution (Fe matrix), and new calibration graphs for each analysis series.
• Performance criteria: Detection limits and precision requirements are specified:
  • Limit of detection: better than 0.05 µg Cr/mL (357.9 nm) and 0.15 µg Cr/mL (425.4 nm).
  • Characteristic concentration: better than 0.2 µg Cr/mL (357.9 nm) and 0.5 µg Cr/mL (425.4 nm).
  • Repeatability requirements for absorbance measurements are defined (e.g., standard deviation limits for calibration readings).
• Safety & quality: Warnings on acetylene handling, UV shielding, burner maintenance and routine blank tests are included.

Practical applications and users

ISO 10138:1991 is used for:

• Quality control and composition certification in steelmaking and iron foundries.
• Metallurgical laboratories performing routine elemental analysis of steels and cast irons.
• Third‑party testing and regulatory compliance where standardized chromium determination is required.
• R&D and failure analysis when accurate Cr quantification in low‑alloy matrices is needed.

Users typically include materials testing labs, steel producers, inspection bodies, and metallurgists focused on alloy composition control.

Related standards

Normative and referenced standards include ISO 377 / ISO 377‑2 (sampling), ISO 3696 (water), ISO 385‑1, ISO 648, ISO 1042 (glassware), and ISO 5725 (precision). These support sampling, reagent quality, apparatus class and method precision.