Overview
ISO 4524-6:1988 specifies a simple, reproducible test method to detect residual salts and other conducting impurities in electrodeposited gold and gold-alloy coatings. The method assesses contamination by boiling metal test specimens in water of known electrical conductivity and measuring any increase in conductivity caused by extracted residues. This part of the ISO 4524 series applies to parts made entirely of metal (not composite parts containing plastics) and is intended for engineering, decorative and protective gold coatings.
Key topics and requirements
- Test principle: Boil coated specimens in 100 ml of water with a known low conductivity; measure conductivity before and after extraction. Any increase indicates residual salts or conducting impurities.
- Reagent: Water with conductivity ≤ 100 μS/m at 20 ± 1 °C is required as the extraction medium.
- Apparatus: Use borosilicate glassware reserved solely for this test (examples given in the standard):
- 250 ml round-bottomed flask with reflux condenser for small/typical parts
- Beaker marked at 100 ml with a means to reduce evaporation (e.g., water-cooled lid) for larger parts
- Conductivity meter to measure changes in solution conductivity
- Specimen and sampling: Test portions consist of coated metal parts with a total surface area around 30 cm². Different specimen geometries have tailored handling (cross-section/dimension criteria are specified).
- Clean handling and preparation: Use clean gloves, dedicated glassware and verify apparatus cleanliness before testing. If initial water conductivity exceeds 100 μS/m, repeat with fresh water or new vessel per the procedure.
- Reporting: Test reports must reference ISO 4524-6, state results and expression method, note any unusual observations and any deviations from the standard.
Practical applications
- Quality control in electroplating and finishing operations to ensure coatings are free from conductive contaminants that can affect corrosion resistance, electrical performance or adhesion.
- Incoming inspection for connectors, electronic components, jewelry and decorative metalwork where residual electrolytes may cause functional or aesthetic failures.
- Root-cause analysis during process troubleshooting (e.g., rinse effectiveness, drying or handling contamination).
- Routine supplier qualification and batch verification in manufacturing and plating facilities.
Related standards
- ISO 4524 (series) - Test methods for electrodeposited gold and gold-alloy coatings:
- Part 1: Coating thickness
- Part 2: Environmental tests
- Part 3: Porosity (electrographite)
- Part 4: Gold content
- Part 5: Adhesion
- Part 7: Sheet resistivity
Keywords: ISO 4524-6:1988, metallic coatings, electrodeposited gold, residual salts, conductivity test, gold alloy coatings, test method, conductivity meter, boiling extraction.
Open preview (PDF)Metallic coatings — Test methods for electrodeposited gold and gold alloy coatings — Part 6: Determination of the presence of residual salts
