Water is the natural enemy of industrial coatings during the application phase. High humidity and sudden rain can cause a host of problems, from “blushing” (whitening of the film) to poor adhesion and premature failure. However, construction schedules often cannot wait for the perfect sunny day. At PZSSS, we provide the technical protocols needed to navigate the challenges of the rainy season.
1. The “3-Degree” Rule: Dew Point is Everything The most critical factor in humid weather is the Dew Point.
- The Rule: The substrate temperature must be at least 3°C (5.4°F) above the dew point of the air.
- If the temperature is too close to the dew point, a microscopic layer of moisture will form on the metal, preventing PZSSS Primers from bonding correctly. Always use a digital hygrometer to verify these conditions before starting.
2. Managing Humidity Limits Most high-performance coatings, especially epoxies, should not be applied if the relative humidity (RH) is above 85%.
- Exceptions: Some specialized PZSSS Moisture-Cure Polyurethanes actually require a bit of moisture to harden.
- Warning: For standard coatings, high humidity traps solvents inside the film, leading to a soft, “gummy” finish that will never fully cure.
3. Emergency Protocol: If Rain Hits Mid-Project
- Stop Immediately: If rain starts, stop spraying and cover all open paint cans.
- Assess the Damage: If the paint is still wet, rain will create “craters” on the surface. Once dry, these areas must be sanded down and re-coated.
- Avoid “Trapping” Moisture: Never paint over a surface that “looks” dry but is still cold and damp to the touch. Use an industrial heat blower to ensure the substrate is bone-dry.
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