Overview
ISO 8003:1985 - "Carbonaceous materials used in the production of aluminium - Pitch for electrodes - Measurement of dynamic viscosity" specifies two laboratory methods for measuring the dynamic viscosity of electrode pitch used in aluminium electrolysis. The standard covers test scope, required apparatus, sampling, calibration, measurement procedures and reporting. It is intended to assess both Newtonian and non‑Newtonian pitch behaviour and to provide reproducible viscosity values in millipascal‑seconds (mPa·s).
Key topics and technical requirements
- Two validated methods
- Method A - Ball displacement (sphere) method: Measures time for a defined steel ball to traverse a fixed distance in molten pitch under controlled temperature and load. Applicable to Newtonian pitches; measurement range ≈ 10^2 to 10^4 mPa·s. Temperature for testing must be above softening point but not exceed 180 °C.
- Method B - Rotation of a cylindrical‑conical body (rotational viscometry): Measures shear stress at a chosen rotational speed using a cylindrical‑conical rotor in a cylindrical vessel. Appropriate for Newtonian and non‑Newtonian pitches (including those thermally treated or showing mesophase) and for higher viscosities (≤ 3 × 10^6 mPa·s).
- Apparatus and calibration
- Method A specifies specific components (e.g., 15.00 ± 0.02 mm steel ball, measuring tube with defined internal diameter and length), thermostatted bath, stopwatch and calibration with liquids of known viscosity. Method B uses a motor‑driven rotational viscometer with rotor set, heating jacket and device‑specific calibration tables.
- Precision and repeatability
- Both methods report an error limit of ±1% and prescribe repeated measurements (Method A: five runs, average used).
- Sampling and reporting
- Sampling shall follow ISO 6257. Test reports must include sample ID, method reference, measured viscosity, test temperature, and any deviations or special observations. Units: mPa·s (1 mPa·s = 1 cP).
Applications and users
- Who uses ISO 8003:1985
- Aluminium smelters, electrode manufacturers, quality control and R&D laboratories, materials testing services and standards bodies.
- Why it matters
- Ensures consistent, comparable viscosity data for electrode pitch selection, process control (mixing, impregnation, baking) and product specification. Method B additionally characterizes non‑Newtonian behaviour relevant to high‑temperature treatments and rheological performance.
Related standards
- ISO 6257 - Sampling of pitch for electrodes (referenced for sample handling)
- ISO 6388 - Surface‑active agents - Determination of flow properties with rotational viscometers (related rotational viscometry methods)
Keywords: ISO 8003:1985, pitch for electrodes, dynamic viscosity, ball displacement method, rotational viscometer, carbonaceous materials, aluminium production.