Overview
ISO 3160-2:2015 - "Watch-cases and accessories - Gold alloy coverings - Part 2" specifies standardized test methods to determine fineness, thickness, corrosion resistance and adhesion of gold-alloy coverings applied to watch-cases and accessories (including bracelets permanently attached to the case). Tests apply to significant surfaces (surfaces essential to appearance/serviceability) and to all gold alloy coverings defined in ISO 3160‑1. The document defines reference methods for arbitration and sets accuracy expectations for laboratory and production testing.
Key topics and requirements
- Scope and applicability
- Covers gold-alloy coatings on watch components and attached bracelets; tests are destructive and apply to significant surfaces only.
- Fineness (gold content)
- Multiple acceptable analytical methods: chemical reduction, cupellation (fire assay), SEM/EDS, atomic absorption, spectrophotometry, X‑ray (ISO 3497), ICP, touchstone (approximate) and others.
- Reference methods for arbitration: cupellation and SEM/EDS.
- Required analytical accuracy: indication within ±50 parts per thousand.
- Thickness measurement
- Accepted techniques include microsection (ISO 1463), coulometric anodic dissolution (ISO 2177), beta backscatter (ISO 3543), X‑ray fluorescence (ISO 3497), SEM (ISO 9220), Fizeau interferometry (ISO 3868) and others.
- Measurement accuracy targeted at ±10%. Microsection is the arbitration method for local thickness.
- Corrosion resistance and porosity
- Identifies three corrosion forms: base metal attack at coating gaps, saline/mildly acidic attack (e.g., perspiration), and sulfur-containing agent attack (tarnishing).
- Standardized tests include porosity/continuity checks, synthetic perspiration, neutral salt-spray, thioacetamide and flowers-of-sulfur tests, and nitric acid vapour where applicable.
- Adhesion
- Procedures and criteria for adhesion testing to verify coating durability on substrates.
- Sampling and preparation
- Annexes detail sample separation and implementation of reference methods.
Practical applications and users
- Watch and jewellery manufacturers - quality control and compliance with ISO 3160‑1 requirements.
- Plating shops and coatings suppliers - process qualification, batch acceptance and supplier-customer agreements.
- Independent testing and metrology laboratories - routine and arbitration testing (cupellation, SEM/EDS, microsection).
- Product designers and material engineers - selection of coatings and corrosion-resistant finishes.
- Regulatory bodies and buyers - specification verification for gold alloy content and durability.
Related standards
Keywords: ISO 3160-2:2015, gold alloy coverings, watch-cases, fineness determination, coating thickness, corrosion resistance tests, adhesion testing, watch industry quality control.
Open preview (PDF)Watch-cases and accessories — Gold alloy coverings — Part 2: Determination of fineness, thickness, corrosion resistance and adhesion