Significance and Use
The thickness of a coating is critical to its performance and is specified in many specifications calling for coatings.
These procedures are used for acceptance testing and appear in a few specifications.
Coating thickness instruments are often calibrated with thickness standards that are based on mass and area measurements.
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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
A90/A90M Test Method for Weight [Mass] of Coating on Iron and Steel Articles with Zinc or Zinc-Alloy Coatings
A309 Test Method for Weight and Composition of Coating on Terne Sheet by the Triple-Spot Test
A428/A428M Test Method for Weight [Mass] of Coating on Aluminum-Coated Iron or Steel Articles
B137 Test Method for Measurement of Coating Mass Per Unit Area on Anodically Coated Aluminum
B449 Specification for Chromates on Aluminum
British Standards Institution Documents
BS3597 Electroplated Coatings of 65/35 Tin-Nickel Alloy, Specification for
Acceptance criteria/testing--coatings; Aluminum coatings; Anodic coatings; Average mass per unit area; Brass electrodeposition; Cadmium metals (coating/plating); Chemical analysis; Chromate coatings; Chromium electroplating; Coating thickness; Density--metallic coatings; Electrodeposited coatings; Electrodeposited Cu coatings; Electrodeposited gold coatings; Gravimetric determination; Lead metals/alloys; Lead-tin alloys/coatings; Linear changes/linearity; Mass per unit area; Mechanically deposited coatings; Micrometer measurement; Microroughness; Microscopic examination--metallic/inorganic coatings; Nickel coatings; Phosphate coatings; Planimetric procedure; Silver (electrodeposited); Terne plate; Tin metals/alloys--electrodeposited coatings; Vernier caliper; Weight per unit area;
ICS Number Code 25.220.40 (Metallic coatings)
ASTM International is a member of CrossRef.
Citing ASTM Standards
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