Overview
ISO 4938:2016 - "Steel and iron - Determination of nickel content - Gravimetric or titrimetric method" specifies laboratory procedures for measuring nickel content in steel and iron. The standard covers both gravimetric and titrimetric routes and is applicable to nickel levels from 1 % to 30 % (mass fraction). It defines sample preparation, chemical reagents, apparatus, stepwise procedure, calculation, precision and reporting requirements.
Key topics and requirements
- Scope: Determination of Ni in steel/iron alloys (1–30 % Ni).
- Analytical principle:
- Acid dissolution of a representative test portion.
- Precipitation of nickel as nickel‑dimethylglyoxime (Ni–DMG) (two precipitations: primary and repeat).
- Gravimetric option: dry and weigh the Ni–DMG precipitate.
- Titrimetric option: dissolve precipitate, add excess EDTA (EDTA.Na2) and back‑titrate the excess EDTA with zinc standard, using xylenol orange indicator.
- Determination of residual nickel in filtrates by atomic absorption spectrometry (AAS) (Annex C).
- Interfering elements:
- Cobalt is oxidized (potassium hexacyanoferrate(III)).
- Copper, when present with cobalt, can be removed by controlled‑potential electrolysis.
- Reagents & safety: Uses strong acids including hydrofluoric acid and perchloric acid - both carry explicit hazard warnings in the standard. Reagents (EDTA, dimethylglyoxime solutions, buffers, standard Ni/Zn solutions) and water quality (ISO 3696) are specified.
- Apparatus: Class A volumetric glassware, sintered‑glass filters (ISO 4793 P16), pH‑meter, and electrolysis equipment where required.
- Sampling & test portion: Sampling per ISO 14284; choose test portion so 25–70 mg Ni precipitated for gravimetry, 25–40 mg Ni for titrimetry (example: ~1 g sample for ~3.5 % Ni).
- Documentation: Calculation methods, precision data and test report content are included.
Applications and users
ISO 4938:2016 is intended for:
- Metallurgical and chemical testing laboratories performing quality control of steels and Ni‑bearing irons.
- Manufacturers and purchasers who need to verify alloy composition, for compliance, certification and material traceability.
- Materials engineers and failure‑analysis labs requiring accurate nickel quantification for specification or research.
Practical uses include verifying nickel content in stainless steels and nickel alloys, production QC, incoming material inspection, and support for material specifications.
Related standards
- ISO 14284 - Sampling and preparation of samples for chemical composition
- ISO 3696 - Water for analytical laboratory use
- ISO 4793 - Sintered filters (porosity)
- ISO 648 / ISO 1042 - Laboratory volumetric glassware
Keywords: ISO 4938:2016, nickel determination, nickel in steel, gravimetric method, titrimetric method, dimethylglyoxime, EDTA titration, atomic absorption spectrometry.
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