Overview
EN ISO 22553-7:2021 (ISO 22553-7:2020) specifies a laboratory method for determining the electrical wet-film resistance / wet-film resistivity of electro-deposition coatings (e-coats). Intended primarily for the automotive industry, the standard also covers other industrial applications such as chiller units, consumer products, radiators, aerospace and agricultural equipment. The measurement informs coating deposition behavior including film thickness development, throwing power and deposition performance under defined conditions.
Key topics and requirements
- Measurement principle: Two complementary approaches are defined:
- Method A - apply a constant current and record voltage vs. time.
- Method B - apply a constant voltage and record current vs. time.
- Quantities defined:
- Electrical wet-film resistance (Rw), dynamic Rw,dyn(t) and static Rw,sta(end).
- Electrical wet-film resistivity (ρw) computed from resistance and electrode geometry (ρw = R · A / l).
- Electrical conductivity (reciprocal of resistivity).
- Apparatus & materials:
- Laboratory deposition system with tank recirculation and DC supply (anode/cathode configuration).
- Voltmeter (method A) or ammeter (method B), thermometer (±0.1 °C) and timer (±1 s).
- Rinse using demineralized water as per ISO 23321 to remove excess “cream coat”.
- Test panels: Electrically conductive panels with pre-treatment per ISO 1514, approx. 190 × 105 × 0.75 mm.
- Procedure & repeatability:
- Panels immersed, deposition initiated, electrical readings recorded throughout deposition time.
- Each determination is carried out in duplicate.
- Reporting & supporting material:
- Evaluation of dynamic/static values, conversion to resistivity, precision data and sample calculations are covered.
- Informative annexes include theoretical derivation and sample calculations.
Practical applications - who uses this standard
- Coating formulators: optimize e-coat conductivity for uniform deposition and desired film build.
- Automotive OEMs & suppliers: verify e-coat deposition behavior, quality control and process validation.
- Independent test laboratories: provide standardized, repeatable wet-film resistivity data for clients.
- R&D and troubleshooting teams: assess throwing power, detect deposition anomalies and compare chemistries.
- Regulatory/compliance staff: reference for material acceptance criteria and cross-lab comparisons.
Related standards
- ISO 22553-1 - Electro-deposition coatings - Vocabulary
- ISO 1514 - Standard panels for testing
- ISO 4618 - Paints and varnishes - Terms and definitions
- ISO 23321 - Demineralized water for industrial applications
Keywords: EN ISO 22553-7:2021, ISO 22553-7, electro-deposition coatings, e-coat testing, wet-film resistivity, electrical wet-film resistance, e-coating, paint and varnish standards.