SIST EN ISO 2931:2018 PDF

Overview

EN ISO 2931:2018 (ISO 2931:2017) specifies a rapid, non‑destructive method for assessing the quality of sealed anodic oxidation coatings on aluminium and its alloys by measurement of admittance. The test is designed for coatings sealed in an aqueous medium and is suitable for routine production control and, where agreed between anodizer and customer, for acceptance testing.

Key topics and technical requirements

• Principle: Admittance (the inverse of complex impedance) of a sealed anodic film is measured to infer sealing quality; the anodic coating behaves as a combination of resistive and capacitive elements in an AC circuit.
• Measurement device: Instrument capable of 3 µS to 200 µS range, measuring at 1 000 Hz ± 10 Hz, with two electrodes - a contact screw to the base metal and a pencil‑type probe.
• Cell & electrolyte: Test cell formed by a self‑adhesive rubber ring (~13 mm internal diameter, internal area ≈133 mm²; acceptable range 100–200 mm²) and potassium sulfate aqueous solution at 35 g/L as electrolyte.
• Specimen requirements: Any anodized component can be tested provided there is a sufficient flat area (a circle of about 20 mm diameter) and film thickness > 3 µm.
• Timing & preparation: Preferably measure 1–4 hours after sealing (within 48 hours). Test area must be clean; degreasing and specific cleaning procedures are described when preservatives are present.
• Limitations & comparability: Results from different sealing methods (e.g., hydrothermal vs cold sealing) are not necessarily comparable. Coatings on alloys with >2% Si, >5% Mn or >3% Mg may give non‑comparable results versus more dilute alloys.

Applications and users

• Who uses it: Anodizers, quality control / inspection laboratories, coating engineers, and customers specifying acceptance tests for anodized aluminium components.
• Practical uses: Routine production control to monitor sealing effectiveness, quality checks before subsequent finishing (oiling, waxing, lacquering), and contractual acceptance measurement when agreed. It is useful wherever fast, non‑destructive assessment of sealed anodic coatings is needed.

Related standards

• ISO 2143 - porosity tests on anodic coatings (correlation considerations noted)
• ISO 3210 - acid‑dissolution reference methods for periodic validation
• ISO 2360 - thickness measurement (eddy‑current)
• ISO 7583 - anodizing terms and definitions

Keywords: EN ISO 2931:2018, ISO 2931:2017, anodizing of aluminium, admittance measurement, sealed anodic oxidation coatings, production control, acceptance test, potassium sulfate electrolyte.