ISO 3160-2:2015

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

• ISO 3160-1 (General requirements for gold alloy coverings)
• ISO 1463, ISO 3497, ISO 2177, ISO 3543, ISO 9227, ISO 11426, ISO 12687, ISO 14647, ISO 27874 (referenced measurement and corrosion methods)

Keywords: ISO 3160-2:2015, gold alloy coverings, watch-cases, fineness determination, coating thickness, corrosion resistance tests, adhesion testing, watch industry quality control.