01Application conditions
- Surface temperature — at least 3 °C above the dew point; you can check it in the guide on temperature and dew point.
- Air, surface and paint — within the TDS range: for Teping® epoxy products usually +5 to +40 °C, with application allowed down to −10 °C.
- Relative humidity — up to 85 % for epoxy products; Teping PU-Coat Top, which cures with air moisture, allows 30–98 %.
- No rain or fog, wind no stronger than 10 m/s; in enclosed spaces, supply and exhaust ventilation.
- Air temperature, humidity, dew point and steel temperature are logged at the start of each shift and every 4 hours.
02Wet and dry film
The painter checks the wet film thickness (WFT) with a comb gauge right after application. It gives the future dry film thickness (DFT) through the volume solids (VS):
| Value | Formula |
|---|---|
| Wet film thickness | WFT = DFT × 100 / VS |
| Volume solids after thinning | VS₁ = VS × 100 / (100 + % thinner) |
| Theoretical consumption, l/m² | DFT / (VS × 10) |
| Practical consumption, l/m² | theoretical consumption × 100 / (100 − % losses) |
Losses depend on the shape of the structure, the profile, wind and application method; they are higher on lattice structures than on flat plates.
Consumption and wet film thickness
Enter the dry film thickness and the volume solids from the product TDS. Without losses you get the theoretical consumption, with losses the practical one.
- Wet film thickness
- —
- Theoretical consumption
- —
- Practical consumption
- —
- Total for the site
- —
03Accepting thickness and adhesion
- Dry film thickness is measured with a magnetic or eddy-current gauge to ISO 2808 and ISO 19840.
- The 80/20 rule: the mean is not below nominal, no reading is below 80 % of nominal, and readings between 80 and 100 % of nominal make up no more than 20 %.
- The maximum thickness is limited by the TDS: an overbuilt coat may crack.
- Adhesion is checked by cross-cut to ISO 2409 or by pull-off to ISO 4624; the requirements come from the design.
- The next coat goes on only after the previous one is accepted and within the overcoating interval of the TDS.
04Typical defects and how to avoid them
| Defect | Cause | How to avoid |
|---|---|---|
| Sags and runs | coat too thick, low viscosity, gun too close | hold the gun at 200–400 mm and at right angles, check the WFT |
| Dry spray | gun too far or at an angle, heat, fast solvent | keep the distance, work within the permitted temperatures |
| Flaking | poor preparation, contamination between coats, missed overcoating interval | check cleanliness, keep intervals, abrade an over-cured coat |
| Blisters and pinholes | salts, moisture or oil on the surface, wrong thinner | wash and degrease, check salts, use only the approved thinner |
| Cracking | overbuilt coat, overcoating a wet coat, hot surface | even thickness within the TDS, control the steel temperature |
| Uneven colour and gloss | cold and high humidity, poor mixing | work within limits, mix the components thoroughly |
Sources. ISO 12944, ISO 8501, ISO 8502, ISO 8503, ISO 19840, GOST 9.402, SP 28.13330 and the technical data sheets of Teping® products on tnpgroup.ru. Check project values against the current TDS.
