Overview
ISO 22553-7:2020 defines a laboratory test method for measuring the electrical wet-film resistance and calculating the wet-film resistivity of electro‑deposition coatings (e‑coats). Intended primarily for the automotive sector and other industrial applications (chillers, consumer products, radiators, aerospace, agriculture), the standard describes how to record electrical behaviour during deposition to assess deposition performance, throwing power and film‑thickness development.
Key topics and requirements
- Scope and purpose: Method to determine wet‑film resistivity of e‑coat materials during the deposition process.
- Measurement principle: Two equivalent approaches:
- Method A - constant current (set current, measure voltage vs time);
- Method B - constant voltage (set voltage, measure current vs time).
- Dynamic vs static values:
- Dynamic electrical wet‑film resistance: resistance profile over deposition time.
- Static electrical wet‑film resistance: resistance at the end of a defined deposition period.
- Wet‑film resistivity is calculated from resistance, electrode area and electrode spacing.
- Apparatus & materials: laboratory deposition tank with DC supply and recirculation, voltmeter or ammeter, temperature control (±0.5 °C), timer and standard test panels (approx. 190 × 105 × 0.75 mm). Typical bath temperature range noted (about 25–35 °C).
- Procedure essentials: panel masking to defined coated area (≈280 cm²), duplicate determinations, continuous recording (e.g., every second), rinsing with demineralized water after deposition.
- Evaluation & reporting: compare resistance curves to agreed profiles, include dry‑film thickness where applicable, and report all test conditions (current/voltage, bath temperature, deposition time, stoving, anomalies). Note: precision data is not provided in the standard.
Practical applications and users
- Who uses it: coating formulators, quality control labs, automotive OEMs and tier suppliers, corrosion engineers, and R&D teams developing e‑coat chemistries or optimizing process control.
- Why it’s useful:
- Evaluate deposition uniformity and throwing power across different substrates (important for multi‑metal bodies).
- Detect differences in substrate conductivity or pretreatment that affect coating build.
- Support process qualification, batch acceptance, and comparative product development.
Related standards
- ISO 22553‑1 (Electro‑deposition coatings - Vocabulary)
- ISO 1514 (Standard panels for testing)
- ISO 4618 (Terms and definitions for paints and varnishes)
- ISO 23321 (Demineralized water for industrial applications)
Keywords: ISO 22553-7, electro-deposition coatings, electrical wet-film resistance, e-coat, wet-film resistivity, deposition test method, automotive coatings.