ASTM B767-88(2016)

4.1 The thickness of a coating is critical to its performance and is specified in many specifications calling for coatings.

4.2 These procedures are used for acceptance testing and appear in a few specifications.

4.3 Coating thickness instruments are often calibrated with thickness standards that are based on mass and area measurements.

4.4 The average thickness of a coating on the measured area can be calculated from its mass per unit area only if the density of the coating material is known.

1.1 This guide outlines a general method for determining the mass per unit area of electrodeposited, electroless, mechanically-deposited, vacuum-deposited, anodicoxide, and chemical conversion coatings by gravimetric and other chemical analysis procedures.

1.2 This guide determines the average mass per unit area over a measured area.

1.3 The stripping methods cited are described in specifications or in the open literature or have been used routinely by at least one laboratory.

1.4 The procedures outlined can be used for many coating-substrate combinations. They cannot be used where the coating cannot be separated from the substrate by chemical or physical means as would be the case if white brass were plated with yellow brass.

1.5 In principle, these procedures can be used to measure very thin coatings or to measure coatings over small areas, but not thin coatings over small areas. The limits depend on the required accuracy. For example, 2.5 mg/cm² of coating might require 2.5 mg of coating covering 1 cm², but 0.1 mg/cm² of coating would require 25 cm² to obtain 2.5 mg of coating.

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.