Dry Film Thickness is generally represented as DFT in industries.
The usual dry film thickness (DFT) expected for a spray touch-up paint on automobiles typically ranges between:
- 25 to 50 microns for a single layer, depending on the type of paint and the spraying technique.
- For multiple layers (e.g., primer, basecoat, and clearcoat), the total DFT typically reaches 75 to 125 microns.
Here’s how the layers usually break down:
- Primer: 20–30 microns.
- Basecoat: 15–25 microns.
- Clearcoat: 30–50 microns.
Proper application ensures uniform coverage, durability, and color match, which are critical for aesthetic and protective purposes.
How DFT is measured?
ASTM Methods of Characterization of Organic Top Coat
The DFT (dry film thickness) of all painted components are usually maintained between 80 and 120 μm and are checked with Elcometer. It is a device that works on the principle of electromagnetic induction for non-magnetic coatings on ferrous substrate and works on Eddy current on non-conducting coatings on non-ferrous metal substrates.
They are tested after 7 days of thorough curing. The dry film tests such neutral salt spray (NSS) resistance, humidity resistance, impact resistance and adhesion test are usually carried out according to ASTM specifications viz., B-117, D-2247, D-2794, and D-3359 respectively. All tests are carried out only after 7 days of complete curing of paint films. The control panels of untreated metal covered with the organic coats are also subjected to the dry film characteristic tests along with the treated set of panels.
