Overview
EN ISO 15091:2020 (Paints and varnishes - Determination of electrical conductivity and resistance, ISO 15091:2019) specifies a laboratory method to measure the electrical conductivity, electrical resistance and to derive resistivity of coating materials. The standard covers both water-borne (including electrodeposition) and solvent-borne paints and varnishes and applies to products with conductivity < 5 µS/cm (resistivity > 200 kΩ·cm). It is intended to assess how coating formulations behave in the presence of electric fields - a key factor for electrodeposition and electrostatic processing.
Key Topics and Requirements
- Scope and applicability
- Conductivity measurement typically for water-borne and electrodeposition coatings.
- Resistance measurement typically for solvent-borne coatings.
- Applicable range: conductivity less than 5 µS/cm (resistivity greater than 200 kΩ·cm).
- Measurement principles
- Determination by voltage/current measurement or comparison via a reference (e.g., bridge circuits/Wheatstone bridge).
- Use of alternating current (AC) is recommended to avoid electrolysis and polarization; frequency should be kept as low as practical to reduce cell reactance.
- Two-electrode and four-electrode configurations are described.
- Apparatus and calibration
- Instruments must be calibrated (see Annex A). Measuring cells require a known cell constant and electrodes made from inert, easy‑to‑clean materials (e.g., stainless steel, platinum, graphite, titanium).
- Ensuring complete immersion and appropriate sample viscosity/conditioning is part of the procedure.
- Test conditions and reporting
- Defines test conditions, sample preparation and number of determinations.
- Includes guidance on expression of results, precision and temperature dependence (Annex B).
Practical Applications and Users
- Who uses EN ISO 15091:2020:
- R&D and formulation chemists developing electrodeposition or electrostatically applied coatings.
- Quality control laboratories checking batch-to-batch conductivity/resistance.
- Suppliers of raw materials (additives/solvents) concerned with electrical properties.
- Coating application engineers ensuring processability in electrostatic or cathodic/anodic deposition.
- Practical benefits:
- Ensures consistent electrostatic behavior and processability.
- Helps diagnose formulation issues (e.g., ionic contamination, solvent effects) that affect deposition or finish quality.
- Supports compliance and comparability across labs by defining measurement method and calibration.
Related Standards
Keywords: EN ISO 15091:2020, electrical conductivity, electrical resistance, resistivity, paints and varnishes, electrodeposition, electrostatic processing, measuring cell, cell constant, conductivity measurement.
