Overview
EN ISO 4524-3:2021 - “Metallic coatings - Test methods for electrodeposited gold and gold alloy coatings - Part 3: Electrographic tests for porosity” specifies four electrographic test methods used to detect and assess porosity in electrodeposited gold and gold-alloy coatings for engineering, decorative and protective applications. The standard is part of the ISO 4524 series and is endorsed by CEN (European Standard EN ISO 4524-3:2021).
Key topics and technical requirements
- Scope: Defines four electrographic porosity tests for electrodeposited gold and gold-alloy coatings.
- Test methods included:
- Nioxime paper test - suitable for gold coatings over nickel or tin‑nickel undercoats. Key procedural points: soak paper in 8 g/l nioxime solution, use moistened blotting paper, compress assembly uniformly at 1.4–1.7 MPa, apply DC voltage ≤ 12 V at an initial current density of 7.5 mA/cm for 30 s. Defects show as pink stains after exposure to ammonia vapour (green stains indicate defects in nickel/tin‑nickel undercoats on copper).
- Dye‑transfer paper test (Test 1) - suitable for gold coatings on copper. Prepare dye‑transfer paper by soaking for 30 min in a 0.01 mol/l NaCl + 0.01 mol/l Na2CO3 solution (0.58 g NaCl + 1.06 g Na2CO3 per litre), blot and proceed per procedure.
- Dye‑transfer paper test (Test 2) - a variant method for specific substrate/coating conditions (method details are provided in the standard).
- Electrographic gelatine film test - uses gelatine film, electrolyte solution and indicators (e.g., dimethylglyoxime) with defined electrolytic, drying and evaluation steps to reveal porosity.
- Materials and reagent quality: Recommends analytical-grade reagents and distilled or equivalent purity water.
- Removed content: The earlier cadmium sulphide paper test was deleted due to restrictions on cadmium use.
Applications
- Quality control for electroplating and finishing operations to detect pinholes, porosity pathways and undercoat exposure.
- Acceptance testing in decorative, electronic, and corrosion‑protective gold plating (e.g., connectors, jewelry, precision parts).
- Failure analysis to pinpoint localized coating defects that could lead to corrosion or electrical failures.
- Process validation when changing plating chemistry, undercoat systems, or operating parameters.
Who should use this standard
- Plating laboratories and quality assurance teams
- Coating and surface‑engineering engineers
- Manufacturers of electronic contacts, connectors and jewelry
- Test laboratories performing porosity and adhesion assessments
Related standards
- Other parts of the ISO 4524 series (see ISO catalogue for the complete list). For national implementation, consult CEN/ISO member bodies and the endorsed EN version (EN ISO 4524-3:2021).
Keywords: EN ISO 4524-3:2021, electrodeposited gold, gold alloy coatings, porosity tests, electrographic tests, nioxime paper test, dye-transfer paper, gelatine film test, electroplating quality control.