Overview
ISO 4524-3:2021 - "Metallic coatings - Test methods for electrodeposited gold and gold alloy coatings - Part 3: Electrographic tests for porosity" specifies four electrographic methods to assess the porosity of electrodeposited gold and gold‑alloy coatings used for engineering, decorative and protective applications. The document replaces the 1985 edition and removes the cadmium‑sulphide paper test because of current restrictions on cadmium use.
Key topics and requirements
- Scope: Defines four electrographic porosity tests for electrodeposited gold and gold‑alloy coatings.
- Test methods included:
- Nioxime paper test - suitable for gold on nickel or tin‑nickel undercoats; uses nioxime‑soaked paper, compression (1.4–1.7 MPa), DC (≤12 V) and an initial current density of 7.5 mA/cm for 30 s. Defects show as pink stains (green for undercoat defects on copper).
- Dye‑transfer paper test 1 - suitable for gold on copper; uses dye‑transfer paper soaked in 0.01 mol/L NaCl + 0.01 mol/L Na2CO3, 4 V DC for 30 s, then development in a saturated ethanolic dithiooxamide solution; defects appear olive‑green.
- Dye‑transfer paper test 2 - a variant of test 1 that uses a 0.5% ethanolic nioxime developer; generally more sensitive than nioxime paper test.
- Electrographic gelatine film test - electrolyte thickened with gelatine and a colour indicator (dimethylglyoxime) for curved surfaces and reduced spot spreading; typical electrolysis is 20 s at 1.0 mA/cm². Test solution and reagent preparation details (gelatine concentration, electrolyte, indicator) are specified.
- Materials and reagents: Use analytical‑grade chemicals and distilled (or equivalent) water; specified reagent recipes, soaking and development steps are provided.
- Procedure controls: Surface cleaning (degreasing), controlled compression, specified voltages/current densities and durations, temperature control for gelatine tests, and post‑test development/rinsing.
- Sensitivity notes: Dye‑transfer and gelatine film methods are noted as more sensitive for detecting microporosity than basic paper electrography.
Applications and users
- Practical for quality control and acceptance testing of electroplated gold and gold‑alloy coatings in:
- Electronics (contacts, connectors)
- Decorative finishes (jewellery, trim)
- Protective coatings in engineering components
- Typical users: plating laboratories, surface‑engineering technicians, QA/QC engineers, materials laboratories, standards writers and procurement/specification teams.
Related standards
- Part of the ISO 4524 series for electrodeposited gold coatings. Developed by ISO/TC 107 (Metallic and other inorganic coatings) in collaboration with CEN. For complete series context and other parts, consult the ISO catalogue.
Keywords: ISO 4524-3:2021, electrodeposited gold, gold alloy coatings, porosity tests, electrographic tests, nioxime paper, dye-transfer paper, gelatine film test, electroplated coatings, microporosity.
Open preview (PDF)Metallic coatings — Test methods for electrodeposited gold and gold alloy coatings — Part 3: Electrographic tests for porosity
