Overview
ISO 1169:2006 specifies a titrimetric method for the determination of aluminium in zinc alloys. Applicable to products covered by ISO 301, the method is suitable for measuring aluminium mass fractions in the range 3 % to 30 %. The procedure is a classical EDTA-based titration using a standard zinc solution and is intended for routine laboratory analysis and quality control in metallurgy and alloy production.
Key topics and technical requirements
- Analytical principle: An excess of EDTA is added to an acid solution of the test portion. The excess EDTA is quantified by titration with a standard zinc solution. The aluminium–EDTA complex is then decomposed (with sodium fluoride) to liberate EDTA, which is titrated again with the standard zinc solution to determine the aluminium-bound EDTA.
- Test portion and reagents: Typical test portion is 5 g. Reagents specified include hydrochloric and nitric acid, hydrogen peroxide, hydroxylammonium chloride, EDTA solution, sodium fluoride (saturated), sodium acetate buffer, methyl red/xylenol orange indicators and a 0.05 M zinc standard solution. All glassware must be cleaned with aqua regia prior to use.
- Procedure highlights: Dissolution in diluted HCl, oxidation with H2O2, neutralization, buffering, heating steps (boil 2–3 min), and color-indicator end-points for titration are specified to ensure reproducible results.
- Calculation & expression: Aluminium content is calculated from the volume (mL) of zinc titrant used to titrate the liberated EDTA using simplified formulae provided for aluminium ≤ 15 % and > 15 %.
- Precision and validation: Interlaboratory trials (13 labs) established repeatability (r) and reproducibility (R) limits that vary with aluminium content (e.g., for 10 % Al: r ≈ 0.078 %; R ≈ 0.175 %). Precision relationships are provided and documented graphically in the standard.
Applications and users
- Who uses it: Metallurgical labs, foundries, alloy manufacturers, quality control/assurance teams, and testing laboratories analyzing zinc alloy ingots and cast products.
- Practical applications:
- Routine compositional analysis of zinc-aluminium alloys (ZA alloys).
- Incoming material inspection and production QC to verify aluminium mass fraction against specification.
- Supporting material certification and product conformity where ISO 301 applies.
- The method is especially useful where a robust, chemistry-based EDTA titration offers a cost-effective alternative to instrumental methods (e.g., spectrometry) for mid-range aluminium contents.
Related standards
- ISO 301 - Zinc alloy ingots intended for casting (product specifications)
- ISO 20081 - Sampling of zinc and zinc alloys
- ISO 5725-1 / -2 / -3 - Accuracy (trueness and precision) of measurement methods and interlaboratory precision assessment
Keywords: ISO 1169:2006, zinc alloys, aluminium determination, titrimetric method, EDTA titration, standard zinc solution, repeatability, reproducibility, metallurgical quality control.
