The correct application of industrial coatings is essential to ensure anti-corrosive protection, mechanical resistance and durability of painted surfaces. Critical factors in application include controlling the wet film thickness (WFT), a fundamental parameter to avoid waste and ensure the expected performance of the paint.
Why control wet thickness?
Controlling wet thickness has a direct impact on paint quality, as it influences:
✔ Adhesion to the substrate
✔ Drying time
✔ Ink consumption
✔ Mechanical and chemical resistance
✔ Reduction of waste and operational costs
If the thickness is below the recommended level, the surface protection will be insufficient, compromising the durability of the coating. On the other hand, a thickness above the specified level can lead to defects such as sagging, prolonged curing time and material waste.
How to calculate wet thickness?
The wet thickness can be determined from the desired dry thickness using the following formula:
WFT=DFTS×100WFT = \frac{DFT}{S} \times 100WFT=SDFT×100
Where:
• WFT = Wet Film Thickness in micrometers (µm)
• DFT = Dry Film Thickness recommended in the project, in micrometers (µm)
• S = Solids by volume of paint (%)
Practical example:
Suppose a paint has 60% solids by volume and the specification calls for a dry film thickness (DFT) of 100 µm. The wet film thickness calculation will be:
WFT=10060×100WFT = \frac{100}{60} \times 100WFT=60100×100 WFT=167µmWFT = 167 µmWFT=167µm
This means that the paint must be applied at 167 µm wet thickness to ensure the desired dry thickness after the solvents have evaporated.
Effective method for saving paint:
To avoid waste and ensure efficient application, follow these guidelines:
1. Use a Wet Thickness Gauge
• The Wet Film Gauge allows you to check in real time whether the application is within the specified range, avoiding paint overload or underapplication.
2. Adjust Application Parameters
• Spray pressure and flow: Setting the correct pressure reduces waste and improves ink transfer to the substrate.
• Distance from nozzle to substrate: Maintaining an ideal distance prevents uneven application.
• Number of coats: Excessive applications generate losses due to runoff.
3. Choose the Right Tool
• For airless painting, choosing the correct nozzle directly impacts savings and thickness control.
• When applying with a roller or brush, choose high retention materials for better coverage.
4. Consider the Transfer Rate
Different application methods have varying efficiencies, which affects paint consumption:
• Brush or roller: 90% to 95% efficiency
• Conventional spray: 30% to 50% efficiency
• Airless Painting: 60% to 80% efficiency
The more efficient the method, the less waste!
Calculating wet thickness is essential to ensure paint performance and savings. Applying a correct WFT prevents protection failures and reduces operating costs, increasing productivity and ensuring that the coating fulfills its function.
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