Overview
ISO/TR 5602:2021 - "Sources of error in the use of electrochemical impedance spectroscopy for the investigation of coatings and other materials" is a Technical Report from ISO that catalogs common measurement errors and artefacts encountered when using electrochemical impedance spectroscopy (EIS) on coated and uncoated materials. It covers the entire measurement workflow - from sample and measuring cell set-up through instrumentation, parameter selection, non‑stationary conditions, equivalent circuit modelling and evaluation. The report supplements the ISO 16773 series by focusing on practical causes of incorrect interpretation and how to recognize them.
Key topics and technical requirements
The document highlights a broad range of error sources and evaluation considerations, including:
- Measuring cell and sample issues
- Surface roughness and wet spots creating stray conductive paths
- O‑ring compression reducing exposed area and affecting results
- Cell assembly faults and gas inclusions
- Electrode considerations
- Reference electrode placement, shielding, bleeding and contamination
- Counter electrode size and reactivity; gas evolution effects
- Electronics and shielding
- Faraday cage use, cable length and shielding, contact resistances
- Instrument limitations: limit impedance/frequency, switching artefacts, signal‑to‑noise constraints
- Measurement parameters
- Suitable amplitude, adequate frequency range, open‑lead tests, dummy cell guidance
- Repetition rates and temporal resolution for subsequent measurements
- Non‑stationary conditions
- Temperature fluctuations, changes in electrolyte conductivity, swelling, drifting open circuit potential (OCP), substrate corrosion
- Data analysis and interpretation
- Selection and ambiguity of equivalent circuit models (constant phase element, Warburg impedance)
- Measurement uncertainty, plausibility analysis and presentation of EIS data
- Supplementary material
- Informative annexes on coating capacitance and double‑layer effects
Practical applications and users
ISO/TR 5602:2021 is useful for:
- Coating and corrosion researchers using EIS to evaluate barrier properties, degradation and defect detection
- Quality control and R&D laboratories in paints, varnishes and protective coatings industries
- Electrochemical instrument manufacturers and test-cell designers seeking to minimize artefacts
- Engineers and technicians troubleshooting inconsistent or non‑reproducible impedance measurements
Practical outcomes include improved test reproducibility, more reliable interpretation of coating performance, and reduced risk of misidentifying artefacts as material failure.
Related standards
- ISO 16773‑1 to ISO 16773‑4 (Electrochemical impedance spectroscopy on coated and uncoated metallic specimens)
- ISO 4618 (Paints and varnishes - Terms and definitions)
Keywords: ISO/TR 5602:2021, electrochemical impedance spectroscopy, EIS, coatings, measurement errors, impedance artefacts, equivalent circuit, coating capacitance.