During the coating application phase, water is the “natural enemy” of industrial coatings. High humidity and sudden rainfall can lead to a series of issues, ranging from “blushing” (whitening of the paint film) to poor adhesion, and even premature failure of the entire coating system. However, project schedules often do not allow us to wait indefinitely for sunny weather. PZSSS has compiled a set of technical solutions to help you tackle the challenges of construction during the rainy season.
1. **The “3-Degree Rule”: Dew Point is Key**
In humid weather, the most critical factor is the **dew point**.
**Core Principle:** The temperature of the substrate surface must be at least **3°C higher** than the ambient dew point temperature.
If the temperature difference is too small, an invisible microscopic water film can form on the metal surface, hindering the strong bond between **PZSSS primer** and the substrate. Before application, always use a digital thermohygrometer to verify this condition.
2. **Strictly Monitor Humidity Limits**
For most high-performance coatings (especially epoxy types), application should not proceed if the relative humidity (RH) exceeds **85%**.
**Exception:** Certain **PZSSS moisture-curing polyurethanes** actually require a small amount of moisture to harden.
**Warning:** For standard coatings, high humidity can trap solvents within the paint film, resulting in a soft, tacky film that never achieves the desired hardness.
3. **Emergency Plan: What to Do If Rain Strikes Mid-Application?**
**Stop Immediately:** As soon as it starts raining, cease spraying immediately and seal all opened paint containers.
**Assess Damage:** If uncured paint is exposed to rain, the surface will develop crater-like pits. After drying, these areas must be sanded and recoated.
**Never “Cover” Moisture:** Do not apply paint over surfaces that appear dry but still feel cold and damp to the touch. Use industrial heat guns to ensure the substrate is thoroughly dried.
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