EN ISO 14647:2016 PDF

Overview

EN ISO 14647:2016 (ISO 14647:2000) specifies the nitric acid vapour test for determination of porosity in gold coatings on metal substrates. It defines apparatus, reagents, safety considerations and a stepwise procedure to reveal pores and defects in gold electrodeposits, claddings and inlays used mainly on electrical contacts. The method is highly sensitive and intended to show whether porosity is below or above an acceptance level chosen by the user.

Key topics and requirements

• Scope and applicability
  • Suitable for: inlays/claddings with ≥75% gold, electrodeposits with ≥95% gold, and substrates of copper, nickel and common alloys used in electrical contacts.
  • Not suitable for coatings less noble than gold or platinum (e.g., palladium and its alloys) or for gold-flashed palladium.
  • Too severe for coatings < 0.6 µm thickness.
• Test principle
  • Nitric acid vapour at low relative humidity reacts at pore sites; corrosion products appear as discrete spots on the gold surface and are counted (visual/low-power stereomicroscope).
  • Quantitative counting is practical for pore densities up to about 100 per cm²; above that the test is useful for qualitative comparison only.
• Apparatus & arrangement
  • Example: sealed glass desiccator (9–12 L) or equivalent; air-space-to-acid-surface-area ratio ≤ 25:1.
  • Specimen holders must be inert (glass, PTFE); specimens ≥75 mm above liquid, ≥25 mm from chamber walls, measurement areas ≥12 mm apart.
  • Avoid placing structures that cover >30% of liquid surface cross-section.
• Safety & destructiveness
  • Involves concentrated nitric acid vapours - specific safety precautions are required (see clauses on safety). The test is destructive: corrosion products and undercutting make tested parts unsuitable for service.
• Supplementary information
  • Annex A: guidance on exposure times.
  • Annex B: recommended procedure to avoid chlorinated hydrocarbons.

Practical applications and users

• Typical users:
  • Plating and quality-control laboratories
  • Manufacturers of electrical contacts, connectors and precision switchgear
  • Materials engineers and failure analysts assessing coating integrity
• Practical uses:
  • Verifying coating porosity to support acceptance criteria in product specifications
  • Locating and counting pores on complex or curved contact surfaces
  • Comparative testing of plating processes or surface finishes
• Caution: results indicate presence/location of porosity but do not by themselves predict electrical performance unless correlated with service data.

Related standards

• ISO 10308 - Review of porosity tests (other porosity methods)
• ISO 2064, ISO 2079, ISO 2080 - terminology, thickness and coating vocabulary referenced by EN ISO 14647:2016

Keywords: EN ISO 14647:2016, nitric acid vapour test, porosity testing, gold coatings, electrodeposits, metallic coatings, electrical contacts, ISO 10308.