ISO 10216:2017

Overview

ISO 10216:2017 specifies an instrumental method for measuring the image clarity of anodic oxidation (anodized) coatings on aluminium and its alloys. The method uses an optical comb (a sliding combed shutter) and a photo‑receiver to quantify how clearly a surface reflects an image. It applies only to flat, reflective surfaces and can also assess optical evenness and light dispersion of anodic coatings. The instrumental approach provides more repeatable and objective results than visual inspection and is suitable for quality control and dispute resolution.

Key Topics and Requirements

• Principle: A slit illuminated and collimated is reflected from the specimen set at 45°; the reflected slit image is analyzed through a sliding combed shutter and measured by a photo‑receiver.
• Image clarity (C): Calculated as C = (M − m) / (M + m) × 100, where M is maximum light intensity and m is minimum light intensity. Image clarity is expressed as a percentage.
• Optical evenness (E): Expressed as the ratio of transverse and longitudinal image clarity values (E = S / L), indicating surface irregularities.
• Dispersion of light (D): Measured to quantify light scattering by the coating (formula and use are defined for higher classes).
• Apparatus essentials:
  • Specimen set at 45° to incident light
  • Collimating/de‑collimating lenses (focal length ~130 mm)
  • Light source (filament ≤ 0.05 mm)
  • Slit (≈0.02 mm ± 0.01 mm width)
  • Combed sliding shutter with 1:1 transparent/opaque ratio; widths: 0.125, 0.25, 0.5, 1.0, 2.0 mm
  • Photo‑receiver and black glass conforming to ISO 7668
• Specimen preparation: Representative flat area (standard size ~50 × 50 mm), clean, and prepared under the same anodizing/sealing conditions as the product.
• Classification (using 0.5 mm comb, larger of transverse/longitudinal values):
  • S: C ≥ 90 (mirror finishes)
  • A: 90 > C ≥ 70 (glossy)
  • B: 70 > C ≥ 30 (low glossy)
  • C: C < 30 (matt)

Applications and Users

• Quality control in anodizing plants and aluminium finishing lines to monitor surface clarity and uniformity.
• Test laboratories performing objective optical assessments of anodic coatings.
• OEMs and specifiers who require quantifiable finish criteria for parts and architectural components.
• Suppliers and purchasers for acceptance testing and dispute resolution where visual assessments are insufficient.
• R&D and process development to evaluate effects of pre‑treatment, anodizing and sealing on optical performance.

Related Standards

• ISO 10215 - visual chart scale for image clarity (optical comb + lightness scale).
• ISO 7583 - terms and definitions for anodizing of aluminium.
• ISO 7668 - black glass requirements and specular reflectance/gloss measurement.

Keywords: ISO 10216:2017, anodizing, anodic oxidation coatings, image clarity, instrumental method, aluminium, optical evenness, combed sliding shutter, measurement.