Standard · Application and film thickness
ISO 2808
The methods for determining film thickness, wet and dry, destructive and non-destructive.
ISO 2808 is the catalogue of film thickness methods. It describes how each method works, what it suits and how precise it is. Each method has a number, so a specification can name it exactly.
The methods
- Wet film: 1A comb, 1B wheel, 1C dial gauge.
- Dry film: 6A cross-section and 6B wedge cut, which cut into the film; 6C white-light interferometry; 7A magnetic pull-off, 7B magnetic flux and induction, 7C eddy current; 10 ultrasonic; 11 terahertz.
Choosing a method
- Magnetic gauges read non-magnetic coatings on steel. Eddy-current gauges read non-conductive coatings on non-ferrous metal such as aluminium.
- Ultrasonic gauges read coatings on concrete, wood or plastic, where a magnetic gauge cannot work.
- A wedge cut shows each coat on its own when the coats differ in colour, but the film then needs repair.
Specifications rarely ask for ISO 2808 alone. They name a method from it, or a procedure built on it such as ISO 19840 for blast-cleaned steel.
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This page describes the subject of ISO 2808 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ISO. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.