13. Dewpoint Tables

One of the most critical aspects of applied coating quality, as well as corrosivity of atmospheres is the dew point, or the point at which a steel surface becomes wet with condensation. For reference, this Dew Point Table lists Dew Point over a range of relative humidities and air temperatures. To allow a practical safety margin, steel substrate temperature should be at least 3oC above the Dew Point. The Dew Point is the temperature of an air-water vapor mixture at which condensation of water vapor starts, as at that point, the air becomes saturated.

Some solvent-based paints are water intolerant and should not be applied unless the surface is at the specified level above the Dew Point. Some other coatings, which are moisture cured, cannot be applied in conditions of low humidity and high temperature as this affects their curing.

The Dew Point is an important factor in corrosion of metals as it is a major determinant of Time of Wetness. Moisture is required to allow any electrochemical corrosion processes to occur, and is thus one of the most significant criteria used for corrosion modeling.