Ask the Expert Question-and-Answer Archive by Ron Joseph May, 2004 Calculating Coating Coverage Q. I would like to know, on behalf of Saab Aerospace/Saab Aerostructures in Sweden, if there is an easy way to calculate if you want to know roughly how much ready-to-spray paint / m2 / micron (or mil). Of course you have to calculate with a certain amount of spray loss, I guess. A plane sheet of metal has of course a higher transfer efficiency compared to a complex, machine made part. A. Thank you for your e-mail. To calculate coverage of a coating the equation is very simple and is given below: Coverage (ft2/gal) = 1604 ft2/gal/mil x % Volume Solids x %Transfer Efficiency                                                                      DFT (mils) The factor 1604 is the area that one solid gallon can cover when it is applied at a film thickness of 1 mil (0.001"). 1 gal = 0.13368 ft3 = area (ft2) x thickness (ft) 1 ft = 12,000 mils 1 gal/mil = 0.133368 ft3/mil = area ft2 x 1 ft                                                12,000 mil Area ft2/gal/mil = 0.13368 ft3/gal x 12,000 mils/ft = 1,604 ft2/gal/mil Example: The volume solids of a coating is 52% and the transfer efficiency of the spray application is 35%, what is the coverage if you apply the coating dry film thickness is 1.5 mil? Coverage (ft2/gal) = 1604 ft2/gal/mil x % Volume Solids x %Transfer Efficiency                                                                  DFT (mils) Coverage (ft2/gal) = 1604 ft2/gal/mil x 0.52 x 0.35                                                1.5 (mil) = 194.5 ft2/gal If you want to calculate the coverage in metric units the conversion factors are as follows; 1 ft = 0.3048 m 1 US gal = 3.7854 L 1 micron = 10-6 L 1 mil = 25.4 microns 1 m3 = 1,000 L Volume solids and transfer efficiency do not have units. Best wishes, Ron Joseph

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