ISO 7668-2021 PDF

Full title and description

St ISO 7668-2021 — Anodizing of aluminium and its alloys — Measurement of specular reflectance and specular gloss of anodic oxidation coatings at angles of 20°, 45°, 60° or 85°. This standard specifies methods (Methods A–E) for measuring directional reflectance and gloss of flat anodized aluminium samples using defined geometries and instrumentation.

Abstract

ISO 7668:2021 describes standardized procedures for determining specular reflectance and specular gloss of anodic oxidation (anodized) coatings on aluminium and its alloys. It defines four primary measurement geometries (20°, 45°, 60° and 85°) plus an additional 45° narrow‑acceptance‑angle method, the required optical apparatus and reference conditions, and notes application limits (primarily intended for clear anodized surfaces; colour anodized surfaces only when comparing similar colours).

General information

• Status: Published (International Standard).
• Publication date: August 2021 (valid from 17 August 2021 in several national catalogues).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 25.220.20 (Surface treatment).
• Edition / version: Edition 4 (ISO 7668:2021).
• Number of pages: 12 (ISO publication page).

Scope

Specifies methods for measurement of specular reflectance and specular gloss of flat samples of anodized aluminium and its alloys using measurement geometries of 20° (Method A), 45° (Method B), 60° (Method C), 85° (Method D) and an additional narrow‑acceptance 45° method (Method E). The procedures are intended mainly for clear anodized surfaces and may be applied to colour‑anodized surfaces only when comparing samples of similar colour. The standard defines instrument and optical requirements, reference conditions and limitations of application.

Key topics and requirements

• Defined measurement geometries: 20°, 45°, 60°, 85° (Methods A–D) and a narrow‑acceptance 45° method (Method E).
• Distinction between specular reflectance (directional reflected luminous flux) and specular gloss (instrument‑referenced gloss units relative to polished black glass).
• Instrument and optical requirements: reflectometers/photodetectors, defined light sources and filters to approximate CIE spectral response under specified illuminants.
• Reference materials and calibration procedures (polished black glass reference assigned gloss value 100 for the geometries).
• Specimen preparation, measurement area considerations and repeatability/acceptance angle guidance (including narrow acceptance aperture option for certain 45° measurements).
• Application limits and notes: primarily for clear anodized surfaces; caution when using on coloured anodized finishes or textured surfaces.

Typical use and users

Used by anodizing plants, surface‑treatment laboratories, QA/QC and inspection bodies, materials engineers, architectural specifiers, automotive and aerospace coating teams, and instrument manufacturers to verify and specify the optical appearance (gloss/reflectance) of anodized aluminium components. Also referenced by standards writers and procurement specialists when defining acceptance criteria for anodized finishes.

Related standards

Standards commonly used alongside ISO 7668 include ISO 7599 (methods and specifications for decorative and protective anodic oxidation coatings), ISO 2813 (gloss measurement for paints and varnishes at 20°, 60° and 85°), and other surface/coating test standards such as ISO 2360 (coating thickness by eddy‑current) or ISO documents on appearance and colorimetry; these provide complementary test methods and specification frameworks.

Keywords

anodizing; anodic oxidation coatings; aluminium; specular reflectance; specular gloss; gloss units; reflectometer; measurement geometry; 20°; 45°; 60°; 85°; Method A–E; calibration; polished black glass.

FAQ

Q: What is this standard?

A: ISO 7668:2021 is an International Standard that specifies procedures for measuring the specular reflectance and specular gloss of anodic oxidation (anodized) coatings on aluminium at specified geometries (20°, 45°, 60°, 85° and a narrow‑angle 45° method).

Q: What does it cover?

A: It covers measurement geometries, instrument and optical requirements, calibration/reference materials (polished black glass), specimen considerations, and limitations on the use of the methods (primarily for clear anodized surfaces; colour anodized only when comparing similar colours).

Q: Who typically uses it?

A: Anodizers, coating and materials testing laboratories, QA/QC inspectors, specifiers (architectural, automotive, aerospace), instrument manufacturers and procurement/specification authors.

Q: Is it current or superseded?

A: ISO 7668:2021 is the current published edition (Edition 4, published August 2021). It revises earlier versions (including the 2018 and much earlier editions); users should refer to the ISO catalogue entry or their national standards body for confirmation of current status.

Q: Is it part of a series?

A: It is part of the suite of ISO standards addressing anodizing and coating evaluation (for example ISO 7599 for specifying anodic coatings) and is frequently used in conjunction with general gloss/appearance standards (ISO 2813) and other anodizing test methods.

Q: What are the key keywords?

A: Anodizing, anodic oxidation coatings, specular reflectance, specular gloss, gloss units, reflectometer, 20°, 45°, 60°, 85°, calibration, polished black glass.