EN ISO 21968:2005

Foreword
1 Scope
2 Principle
3 Equipment
4 Sampling
5 Factors affecting measurement accuracy
  5.1 Coating thickness
  5.2 Electrical properties of the basis materials
  5.3 Electrical properties of the coating materials
  5.4 Basis-metal thickness
  5.5 Edge effects
  5.6 Surface curvature
  5.7 Surface roughness
  5.8 Lift-off effect
  5.9 Probe pressure
  5.10 Probe tilt
  5.11 Temperature effects
  5.12 Intermediate coatings
6 Procedure
  6.1 Calibration of instruments
  6.2 Determination
7 Expression of results
8 Measurement uncertainty
9 Test report
Annex A (informative) Eddy-current generation in a metallic
        conductor
Annex B (normative) Test for edge effect
Bibliography

ISO 21968:2005 describes a method of using phase-sensitive eddy-current instruments for non-destructive measurements of the thickness of non-magnetic metallic coatings on metallic and non-metallic basis materials such as zinc, cadmium, copper, tin or chromium on steel, as well as copper or silver on composite materials.The phase-sensitive method can be applied without thickness errors to smaller surface areas and to stronger surface curvatures than the amplitude-sensitive eddy-current method described in ISO 2360, and is less affected by the magnetic properties of the basis material. However, the phase-sensitive method is more affected by the electrical properties of the coating materials.