EN ISO 2177:2004 PDF

Overview

EN ISO 2177:2004 (identical to ISO 2177:2003) specifies a coulometric method by anodic dissolution for measuring the thickness of metallic coatings. The method is applicable only to conductive coatings, including multi-layer systems (e.g., Cu–Ni–Cr) and coatings on cylindrical specimens and wires. Thickness is determined from the quantity of electricity (coulombs) required to anodically dissolve a defined test area; an endpoint is detected by a change in cell voltage.

Key topics and technical requirements

• Scope and applicability
  • Designed for conductive metallic coatings; typical coating/substrate pairs are listed in the standard.
  • Other combinations can be tested with existing or newly developed electrolytes, but the suitability of the complete system must be verified before use.
• Principle
  • A sealed measuring area is anodically dissolved in a suitable electrolyte. Thickness is calculated from either constant-current × time or the integrated charge.
  • Endpoint detection relies on a detectable change in electrode potential when the substrate is exposed.
• Instrumentation
  • Proprietary and custom instruments are used (see Annex B). Instruments may give direct readout or provide recorded charge (coulombs) for conversion to thickness.
  • Instruments must be checked against specimens of known thickness; agreement within ±5 % allows use without adjustment.
• Electrolyte
  • Electrolyte selection (Annex A) must ensure high anodic dissolution efficiency, wetting of the test area and a stable shelf-life.
  • Electrolyte choice depends on coating/substrate materials, current density and cell circulation.
• Factors affecting accuracy
  • Coating thickness limits (practical accuracy reduced for >50 µm and