What Is the Best Way to Adjust for Surface Profile When Measuring Dry Film Thickness (DFT)?

Abstract Steel surfaces are frequently cleaned by abrasive impact prior to application of protective coatings. The resulting surface profile creates complications when measuring the thickness of an applied coating using a coating thickness gage. The effect on gage measurements increases with profile depth and also depends on the design of the probe and the thickness of the coating. Various international standards propose different, and often times dissimilar, methods to correct for the effect of surface profile on dry film thickness (DFT) readings. This study intends to analyze and compare different adjustments methods, including those provided in ASTM1 D7091 (1) and ISO2 19840 (2) to determine their accuracy and similarity. A number of different coating thickness gage models will be used to better determine the applicability of each method, and to determine how well the methods apply for varying instruments, probe designs, and measurement range capabilities.