Overview
ISO 23052:2020 specifies a standardized test method to assess the chemical resistance of anodic oxidation (anodized) coatings on aluminium and its alloys using an electromotive force apparatus. The method measures the time it takes for a test solution (alkali or acid) to dissolve the anodic coating by detecting electrical continuity (a voltage rise to 1.0 mV) between the coating/substrate and a stainless-steel cell. The test is suited to whole-coating evaluation, including thick anodic films (>20 μm), and requires only a small test area and small volumes of reagent.
Key topics and technical requirements
- Principle: Dissolving time of the anodic coating is determined by the time from injection of the test solution into an electric-potential cell until the electromotive force detector reads 1.0 mV.
- Test solutions:
- Alkali (sodium hydroxide), two typical concentrations: Type A = 100 g/L, Type B = 40 g/L.
- Acid (phosphoric acid), concentration close to 570 g/L (preparation example in the standard).
- Apparatus essentials: hot plate for temperature control, stainless-steel electric-potential generating cell (316 grade) with internal volume >1 mL, non-conductive gasket (internal diameter ≈ 3.6 mm), electric-potential detector and 1.0 Ω resistor.
- Specimen preparation: representative, flat surface samples (standard size ≈ 50 × 50 mm), cleaned with a suitable solvent (e.g., ethanol) and prepared under the same anodizing/sealing conditions as the product.
- Test conditions: typical surface temperatures - alkali: 35 °C ±1 °C, acid: 80 °C ±1 °C. Measurement uses ~1 mL test solution injected into the cell; repeat at least three positions and report the average, omitting outliers caused by defects.
- Reporting: include reference to ISO 23052, product ID, gasket size (if different), solution type and concentration, temperature, deviations, observations, results and test date.
- Supporting information: Annexes cover alternative conditions (A), heating-up-time validation (B) and relationships with coating dissolution (C).
Applications and users
ISO 23052 is practical for:
- Anodizers validating sealing methods and process changes.
- Quality laboratories measuring alkali/acid resistance of anodized finishes.
- Manufacturers and OEMs of aluminium components (industrial products, electrical appliances, kitchenware) requiring resistance data.
- R&D teams optimizing anodizing parameters and comparing coatings.
The method is useful when small sample areas, minimal reagent use and fast, reproducible assessments are required.
Related standards
- ISO 7583 - terms and definitions for anodizing of aluminium and its alloys (referenced for terminology).
- Annexes in ISO 23052 provide guidance for non-standard concentrations, gasket sizes and validation procedures.
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