Overview
ISO 3613:2021 - Metallic and other inorganic coatings - specifies standardized test methods for chromate conversion coatings on zinc, cadmium, aluminium‑zinc and zinc‑aluminium alloys. The fourth edition (2021) covers qualitative and quantitative determinations including the presence of colourless and coloured chromate coatings, detection of hexavalent chromium (Cr(VI)), total chromium per unit area, coating mass per unit area, adhesion and overall coating quality. The standard applies to coatings produced by chemical or electrochemical processes and to coatings without supplementary oil, polymer or wax layers.
Key topics and requirements
- Presence of colourless chromate coatings: simple detection tests for nearly invisible (passivation) layers on zinc, cadmium and specified aluminium‑zinc/zinc‑aluminium alloys.
- Detection and quantification of hexavalent chromium (Cr(VI)): colorimetric/spectrophotometric procedures (including test solutions C1 and C2) to determine Cr(VI) in both colourless and coloured chromate coatings; includes calibration and spectrophotometer procedures.
- Total chromium content per unit area: methods for measuring total chromium on zinc and cadmium coatings.
- Coating mass per unit area: gravimetric determination following ISO methods for mass-per-area measurement.
- Adhesion and quality tests: abrasion adhesion tests and defined quality-evaluation procedures for chromate layers.
- Reagents and apparatus: prescribes analytical-grade reagents (e.g., diphenylcarbazide, lead acetate, orthophosphoric acid), glassware cleanliness, and use of a colorimeter/photometric absorptiometer with 520 nm filter.
- Safety and regulatory context: notes hazardous nature of Cr(VI); highlights that Cr(VI) use is restricted in jurisdictions such as the EU and that users must follow safety and environmental regulations.
- Alignment with other methods: analysis method in clause 6.5 aligned with IEC 62321‑7‑1; references ISO 3892, ISO 4520 and IEC 60068‑2‑30.
Applications
ISO 3613:2021 is used to:
- Verify conformity of chromate conversion coatings in manufacturing quality control.
- Screen for hexavalent chromium content for regulatory compliance and RoHS/WEEE‑related checks.
- Measure coating mass and total chromium for supplier acceptance and contract testing.
- Assess adhesion and wear resistance for protective finishes on fasteners, stamped parts, fittings and electroplated components.
Who should use this standard
- Coating and surface‑treatment laboratories
- Quality assurance and inspection teams in plating and metal‑finishing industries
- Manufacturers of zinc/cadmium plated parts, fasteners and components
- Regulatory and compliance testing bodies monitoring Cr(VI) content
Related standards
- ISO 3892 - gravimetric coating mass determination
- ISO 4520 - chromate conversion coatings on electroplated zinc and cadmium
- IEC 62321‑7‑1 - analytical methods for Cr(VI) (alignment referenced)
- IEC 60068‑2‑30 - environmental testing (damp heat cycle)
Keywords: ISO 3613:2021, chromate conversion coatings, hexavalent chromium, Cr(VI), zinc coatings, cadmium coatings, aluminium‑zinc alloys, chromating test methods, coating mass per unit area, adhesion test, diphenylcarbazide, spectrophotometer.