Overview
ISO 11713:2025 specifies a laboratory method for determining the specific electrical resistivity of carbonaceous cathode blocks and baked anodes used in aluminium production. The test is carried out at ambient temperature on prepared cylindrical or cuboid samples. The measured resistivity is used to characterise electrical performance in reduction cells, monitor quality (including detection of microcracks), and support process and materials optimisation.
Keywords: ISO 11713:2025, specific electrical resistivity, cathode blocks, baked anodes, aluminium production, carbonaceous materials, resistivity measurement.
Key topics and technical requirements
- Principle: A fixed direct current is passed through the specimen; the voltage drop between voltage sensors is measured to calculate resistivity using the specimen cross-sectional area and sensor spacing.
- Sample preparation:
- Minimum dimensions: Ø 30 mm (cylinder) or 30 × 30 mm (square); length ≥ 100 mm.
- Cross-section variation in the measuring zone: ≤ 0.5% relative.
- Drying: oven at (100 ± 5) °C for at least 2 hours, then cool before testing.
- Apparatus & tolerances:
- Drill and cutter with diamond tooling; slide caliper accurate to ±0.1 mm.
- Ammeter ±0.002 A, voltmeter/potentiometer ±0.001 V.
- Sample clamping device with current contactor and voltage sensors (point or blade sensors radius ≥ 200 µm).
- Contact forces: current contactor ≥ 50 N, voltage sensors ≥ 0.5 N.
- Oven capability: 110 ± 5 °C.
- Geometric placement: sensor distances specified relative to sample width/diameter (e.g., sensors ≥ 0.8 D apart and ≥ 40 mm).
- Measurement conditions:
- Current density limited to 10 000 A/m ± 20 A/m.
- Measure on four orientations (rotate sample 90°) to detect anisotropy or horizontal cracks.
- Calculation & reporting:
- Resistivity calculated from measured voltage (U), current (I), cross-sectional area (A) and sensor spacing (l); results expressed in µΩ·m with rounding rules (nearest integer > 20 µΩ·m, one decimal