The effects of condensation forming on recently applied coating systems can often result in color change, gloss reduction, blistering, loss of adhesion, softening, or embrittlement.
Any material placed on an exposed substrate will try to maintain a moisture content equal to its surroundings. Physical stresses are created as the material loses or gains water content. The greater the range of moisture, the greater the overall stress on the coating.
Dew, condensation, and rain are significant factors in paint degradation when in contact with newly applied conventional coatings. Average time-of-wetness in the United States is approximately 8 hours per day. Coastal regions, such as Tidewater average higher. As the dew or condensation evaporates, the coating undergoes degradation through stress, resulting from wet/dry cycling.
Condensation arises when the temperature drops below the dew point temperature of the surrounding air. This causes water vapor in the air to condense on the coating. The physical and chemical responses of the coating caused by condensation have a greater effect on the coating than rainfall. Condensation moisture has high levels of dissolved oxygen, which accentuates degradation.
The total time the coating is wet from moisture, prior to cure, plays an important factor in the degree and rate of degradation. Prolonged exposure to surface condensation will allow the absorption or permeation of a relatively high level of water and oxygen, and as the day progresses, a strong pressure will be exerted by the atmosphere for water desorption. The longer the intervals of wetting and drying, the deeper into the coating will be the cycle effect. Also the faster the rate of cycling, the more the effect remains at the surface and the less penetration is made into the foundation of the coating.
Proper painting procedures should include awareness of current weather conditions and conditions throughout the entire curing cycle of the specific coating to insure life expectancy of the coating as designed.