Definition - What does Coverage mean?
Coverage refers to the coating spread rate, which is usually expressed in units of square feet per gallon or square meters per liter. The coverage value helps a coating expert determine how much paint or coating is required and what area a given quantity of paint or coating will cover. The Pfund formula, developed by the paint instruments developer George Pfundis, is used to estimate the coverage or the paint spread rate.
Corrosionpedia explains Coverage
Coverage for pigment coatings is related to the hiding power, whereas coverage for clear coatings refers to the area coated at a desired film. According to the Pfund formula, the coverage obtained from a gallon of paint is dependent on its nonvolatile (solids) content. One gallon occupies a volume of 231 cubic inches or 0.1337 cubic feet. If a gallon of paint contained 100% solids and if it could be applied without losses, the coverage obtained from one gallon of paint applied to a film thickness of 1 mil (0.001 inch or 0.0000833 foot) would be 1605 square feet (0.1337 divided by 0.0000833). This figure is expressed as the theoretical coverage per gallon.
The Pfund formula is:
Theoretical Coverage = (Volume Solids) / (Dry Mils Required)
For example, if a coating were 45% solids by volume, its theoretical coverage would be (0.1337/0.0000833) x 0.45 or 722 square feet at 1 mil dry film thickness.
If a specification called for a dry film thickness of 2 mils, the theoretical coverage would then be 722 square feet divided by 2 mils, or 361 square feet per gallon.
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