ISO 2376:2019

Overview

ISO 2376:2019 - "Anodizing of aluminium and its alloys - Determination of breakdown voltage and withstand voltage" specifies laboratory test methods to determine the electrical insulating performance of anodic oxidation (anodized) coatings on aluminium and its alloys. The standard covers tests on flat or near‑flat surfaces and on round wire, measuring the voltage at which the coating breaks down (breakdown voltage) and the voltage the coating can sustain for a specified time (withstand voltage). ISO 2376:2019 is intended for anodic oxidation coatings used primarily as electrical insulators.

Key topics and technical requirements

• Scope and limitations
  • Applies to anodic coatings on flat/near‑flat surfaces and round wire; not applicable near cut edges, hole edges or sharp angle changes.
  • Results are sensitive to relative humidity and sealing; unsealed coatings give unreliable results.
• Test principle
  • Measure the voltage at which current first flows through the anodic coating (breakdown) and the ability to hold a specified voltage for a given time (withstand).
• Apparatus and setup
  • AC power supply (50 Hz or 60 Hz) with transformer and voltage regulator providing an essentially undistorted waveform.
  • Current limiting resistor (0.5 MΩ) in series and a spherical electrode probe (3–8 mm diameter) applying 0.5–1.0 N force.
  • Contact plate/clip to contact the base metal for flat specimens; twisting machine and specified number of twists per 50 mm for round wire tests.
• Procedure and parameters
  • Precondition specimens in test environment for ≥1 hour; record temperature and relative humidity (default: room temperature and <65% RH).
  • Increase voltage uniformly at a rate not exceeding 25 V/s for breakdown tests.
  • Perform a minimum of five tests; report the lowest and mean breakdown voltages and/or the specified withstand voltage and duration.
• Reporting
  • Test report must reference ISO 2376:2019 and include product ID, anodizing specification, test environment conditions, breakdown/withstand results and any anomalies.

Applications and users

ISO 2376:2019 is practical for:

• Quality control in anodizing plants and finishing shops
• Electrical and electronics manufacturers specifying insulated aluminium parts or wires
• R&D and materials labs evaluating dielectric performance of anodic coatings
• Procurement/specification writers and conformity assessors who require standardized insulation test data

Key benefits: standardized, repeatable measurement of dielectric strength for anodized aluminium, supporting product acceptance, failure analysis and specification compliance.

Related standards

• ISO 7583 - Anodizing of aluminium and its alloys: Terms and definitions (normative reference for ISO 2376:2019).