Overview - ISO 26202:2019 (Magnesium alloys for cast anodes)
ISO 26202:2019 specifies grades and delivery requirements for magnesium alloy ingots and cast magnesium anodes used as galvanic (sacrificial) anodes. The standard defines material designations, casting-process symbols, chemical composition limits for each alloy grade, sampling and testing procedures (including electrochemical tests), and requirements for packaging and surface protection.
Key topics and technical requirements
- Material designations: Grades are designated by symbol or number (examples: ISO-MBMgAl3Zn1, ISO-MAMgA3Zn1). Casting-process symbols: S = sand casting, K = permanent mould (gravity), C = continuous casting.
- Chemical composition: Tables set minimum/maximum mass fractions for major elements (Al, Zn, Mn) and limits for impurities (Si, Fe, Cu, Ni, etc.) for both ingots and castings. Example ranges include:
- Mg–Al–Zn alloys (e.g., ISO‑MB/MAMgAl3Zn1 and MgAl6Zn3) with specified Al, Zn, Mn ranges.
- Mg–Mn alloys with defined Mn minimums (e.g., 0.5 % and 1.2 % classes) and tight limits on other elements.
- Potable water specification: For anodes used in drinking water, contaminant limits are required: (As + Pb + Cr(VI) + Ni) ≤ 0.1% and (Cd + Sb + Se + Hg) ≤ 0.01% (mass fraction).
- Sampling and chemical analysis: Samples shall be representative and taken from molten metal at casting. Chemical analysis methods shall follow standardized or validated procedures (note: ASTM B953 and ASTM B954 are identified as acceptable references).
- Electrochemical testing (Annex A & B):
- Annex A: Electrode potential measured in 0.0010 mol·L−1 NaCl at (60 ± 3) °C using galvanostatic polarization; recommended average potential more negative than −0.9 V vs SHE at 50 μA/cm² to avoid passivation.
- Annex B: Mass-loss test in 0.01 mol·L−1 NaCl at (60 ± 3) °C with galvanostatic 50 mA/cm²; mass loss inferred from hydrogen evolution.
- Packaging/surface protection: Manufacturer must provide protection to prevent damage, contamination or corrosion during transport and storage unless otherwise agreed.
Applications and who uses this standard
- Manufacturers and foundries producing magnesium ingots and cast sacrificial anodes for cathodic protection.
- Designers and specifiers in marine, pipeline, underground storage tank, and water utility industries requiring reliable galvanic anodes.
- Quality assurance teams and testing laboratories performing chemical and electrochemical verification.
- Purchasers and procurement specialists ensuring compliance with material grade, casting process, and potable‑water requirements.
Related standards
- EN 1559-1 and EN 1559-5 (technical delivery conditions for castings)
- ISO 80000-1 (quantities and units)
- ASTM B953 / B954 (examples of chemical analysis procedures)
Keywords: ISO 26202:2019, magnesium alloys, cast anodes, chemical composition, electrode potential, mass loss test, galvanic anode, casting processes, potable water anodes, electrochemical testing.
