Metal Finishing Guide Book


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should be used along the length, not the width, of curved surfaces. Using a wetfilm gauge on quick-drying coatings (inorganic zinc, vinyls, etc.) will yield in accurate measurements. ASTM D 4414 outlines a standard method for measurement of wet-film thickness by notch gauges. THICKNESS STANDARDS Coating thickness gauges are calibrated to known thickness standards. There are many sources of thickness standards but care must be taken to ensure they are traceable to a national measurement institute such as NIST. It is also important to verify that the standards are at least four times as accurate as the gauge they will be used to calibrate. A regular check against these standards verifies the gauge is operating properly. When readings do not meet the accuracy specification of the gauge, the gauge must be adjusted or repaired and then calibrated again. 607

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