The dew point is the temperature below which water vapor condenses as dew. The higher the temperature, the more water vapor the air can absorb. As the temperature declines, so does the capacity of the air to absorb moisture, so the water vapor condenses out as liquid.
This phenomenon plays a major role in corrosion protection: If the surface isn’t completely dry during the coating process, the paint’s adhesive properties can be severely restricted.
The dew point is determined by the temperature and the relative humidity. The decisive factor here is the temperature of the object: If its surface is colder than the ambient air, moisture will condense onto it – even if the relative humidity is far below 100%. According to DIN EN ISO 12944, the temperature of the object must therefore be at least 3°C higher than the dew point during the entire coating process.