Overview
ISO 3981:1977 specifies an atomic absorption spectrophotometric (AAS) method for the determination of nickel (Ni) in aluminium and aluminium alloys. The method is applicable to nickel contents between 0.005% and 3% (m/m) and defines principle, reagents, apparatus, sampling, procedure, expression of results and test report requirements.
Key topics and technical requirements
- Scope and ranges: Method covers Ni contents from 0.005 to 3 % (m/m).
- Analytical principle: Dissolve a test portion in hydrochloric acid (with hydrogen peroxide if required), atomize in an air–acetylene flame and measure nickel absorption at a resonance wavelength (normally 232.0 nm).
- Reagents: Uses analytical-grade reagents such as hydrochloric acid, hydrogen peroxide, sulfuric acid, hydrofluoric acid, nitric acid and matrix aluminium solutions. Nickel standard solutions are prepared (examples given corresponding to 0.125 g Ni·L⁻¹ and 0.025 g Ni·L⁻¹) and diluted for calibration.
- Apparatus: Standard laboratory glassware plus an atomic absorption spectrophotometer fitted with an air–acetylene burner and a nickel hollow‑cathode lamp; a burette for precise standard dispensing.
- Sampling and test portion: Test samples should be chips ≤ 1 mm thick. Typical test portion mass is 1 g (weighed to 0.001 g) for the procedure described.
- Calibration and measurement: Matrix‑matched calibration curve is prepared using specified standard solutions mixed with an aluminium base solution. Reference solutions are atomized and measured; the sample and blank are measured under the same conditions.
- Calculation and reporting: The standard provides the formula to convert measured nickel mass into percentage by mass and prescribes the content of the test report (method reference, results and form, any special observations and optional operations). Confidence interval procedures were noted as under study.
Applications and users
ISO 3981 is practical for:
- Quality control and chemical analysis laboratories in aluminium production and alloys processing
- Metallurgical test labs verifying alloy composition for aerospace, automotive, electronics and general engineering applications
- Third‑party testing and conformity assessment bodies checking compliance with material specifications
- R&D groups and process control teams monitoring nickel impurity levels
This standard supports reliable quantification of nickel where small concentrations can affect alloy properties or specification compliance.
Related standards
- Work was prepared by ISO/TC 79 (Light metals and their alloys). A separate ISO standard for sampling of aluminium and aluminium alloys was indicated as forthcoming at the time of ISO 3981’s publication.
- Complementary standards include other ISO and national methods for elemental analysis and AAS operating procedures (refer to current ISO catalogues for updated references).