The bottom line
ISO 2808:2019 does not teach you how to operate the gauge; what it does is draw the map: it classifies paint film thickness measurement by state and tells you which specific method standard to reference.
Key facts
| Item | Content |
|---|---|
| Number | ISO 2808:2019 (updated 2019-07-26) |
| Status | Umbrella standard |
| Coverage | All measurement methods for wet film, dry film, powder coatings and rough-surface coatings |
| Chinese equivalent | GB/T 13452.2 |
| Referenced by | ISO 19840, ISO 12944, ASTM D7091, ASTM D6132, SSPC-PA 2, etc. |
Four categories of measurement methods
① Wet film thickness (WFT)
Measured before the coating cures, used for process monitoring. The common method is a wet film comb (notch gage) — a metal strip with teeth of different depths; pressed into the wet film, you read the thickness by seeing which teeth touch bottom. Wet film is not the basis for final acceptance.
② Dry film thickness (DFT)
The thickness after the coating is fully cured; it is the main body of acceptance. ISO 2808 points here to several method standards: magnetic method (ISO 2178), eddy-current method (ISO 2360), ultrasonic method (ISO 19397), micrometer method.
③ Uncured powder coating
Thickness control of the powder after spraying but before curing, using a powder comb or a pre-calibrated magnetic gauge. This step avoids rework after curing.
④ Coating on rough substrates
Rough surfaces such as blasted steel need more spots and a baseline correction; the specific clauses reference ISO 19840.
Why it is called the “common language”
In a technical document or product description, if you cannot determine which method the customer uses, referencing ISO 2808 is the broadest possible statement — because it includes magnetic, eddy-current and ultrasonic methods at once. This is also its practical value in cross-industry communication.
Correspondence with the ASTM system
ISO and ASTM correspond closely on paint film thickness measurement, but the reference format and acceptance details differ. For cross-market work, choose by project location:
| Content | ISO system | ASTM / SSPC system |
|---|---|---|
| Dry film magnetic method | ISO 2178 | ASTM D7091 |
| Dry film eddy-current method | ISO 2360 | ASTM D7091 |
| Paint film thickness general spec | ISO 2808 | ASTM D7091 / D6132 |
| Rough-surface acceptance | ISO 19840 | SSPC-PA 2 |
| Ultrasonic coating thickness | ISO 19397 | ASTM D6132 |
Common misconceptions
- ❌ “ISO 2808 can be used directly as the acceptance basis” — it does not set an acceptance threshold itself; judgment needs a specific standard or project specification.
- ❌ “Wet film and dry film are the same” — the measurement method, instrument and purpose of wet and dry film are completely different; the former is for process control.
- ❌ “GB/T 13452.2 is an independent national standard” — it identically adopts ISO 2808, an adoption relationship.