ASTM B137-95(2021)

• Abstract:

  SIGNIFICANCE AND USE; 3.1 This test method is a destructive test procedure suitable for quality control within manufacturing operations for coating mass on anodically coated aluminum and aluminum alloys. The mass of the coating is an approximation of its thickness provided the conditions under which the coating was applied, or the density of the coating, are known. An anodic coating's protective value and amenability to coloring by dying or electrolytic methods are related to mass of coating per unit area.; SCOPE; 1.1 This test method covers determination of the mass per unit area of coating on anodically coated aluminum and its alloys. ; 1.2 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. ; 1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

• Status: Published
• Publication Date: 30-Sep-2021
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.07 - Conversion Coatings

• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999

Overview

ASTM B137-95(2021) - Standard Test Method for Measurement of Coating Mass Per Unit Area on Anodically Coated Aluminum is an internationally recognized testing method developed by ASTM International. It provides a destructive procedure for determining the mass of anodic coatings-commonly applied to aluminum and aluminum alloys-to support quality control in manufacturing operations. By accurately measuring the mass per unit area, this test method enables manufacturers to estimate coating thickness, assess protective properties, and verify compliance with product specifications.

This method is endorsed by leading industry organizations such as the American Electroplaters’ Society and the National Association of Metal Finishers, and is approved for use by agencies of the U.S. Department of Defense.

Key Topics

• Purpose and Significance

  • Assures the quality and consistency of anodic coatings by providing a direct measurement of coating mass per unit area.
  • The mass is an approximation of coating thickness if the application conditions or coating density are known.
  • Coating mass is related to key functional properties, including corrosion resistance and improved coloring ability (via dyeing or electrolytic methods).

• Test Method Outline

  • The test involves removing the anodic coating from a pre-measured test specimen, using a specified chemical solution (phosphoric-chromic acid).
  • Precise weighing before and after stripping the anodic layer allows for the calculation of the coating mass per square decimetre.
  • The procedure is destructive, meaning the test piece cannot be used in production after testing.

• Applicability and Safety

  • Suitable for anodically coated aluminum and its alloys in manufacturing environments.
  • The user is responsible for implementing appropriate safety, health, and environmental practices, and for understanding regulatory requirements.

Applications

• Quality Assurance in Manufacturing

  • Helps manufacturers monitor and control anodizing processes, ensuring consistent product performance.
  • Enables verification that anodic coatings meet specified thickness or mass requirements for finished aluminum components.

• Performance Evaluation

  • Used to evaluate the durability and effectiveness of anodic coatings in protecting aluminum from corrosion and wear.
  • Provides data for research and development of improved surface finishing techniques.

• Compliance and Certification

  • Supports demonstration of compliance with customer specifications, industry standards, and regulatory bodies.
  • Widely adopted in the aerospace, automotive, architectural, and electronics sectors for critical aluminum parts.

Related Standards

• ASTM D1193 - Specification for Reagent Water

  • Specifies water quality for reagent use, referenced for preparing test solutions in B137.

• Other Anodic Coating Standards

  • Standards related to the thickness, sealing, and other properties of anodic coatings on aluminum may be applicable in conjunction with B137, such as those from ISO, MIL, or additional ASTM specifications.

• International Standardization Principles

  • Developed in alignment with the World Trade Organization’s Technical Barriers to Trade (TBT) Committee’s guidelines for international standards, supporting global compatibility and acceptance.

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Keywords: ASTM B137, coating mass, anodically coated aluminum, anodic coatings, test method, quality control, aluminum alloys, surface finishing, corrosion protection, manufacturing standards, industrial anodizing.

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B137 − 95 (Reapproved 2021) Endorsed by American
Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Test Method for
Measurement of Coating Mass Per Unit Area on Anodically
Coated Aluminum
This standard is issued under the fixed designation B137; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 4. Reagents
1.1 This test method covers determination of the mass per 4.1 The test solution shall have the following makeup:
unit area of coating on anodically coated aluminum and its
Chromic acid anhydride (CrO ) 20±0.5 g
Orthophosphoric acid of 85 mass %, density
alloys.
1.69 35 ± 0.5 mL
1.2 This standard does not purport to address all of the
Distilled or deionized water conforming with
Type III Reagent Water of Specification
safety concerns, if any, associated with its use. It is the
D1193, to make up to 1000 mL
responsibility of the user of this standard to establish appro-
NOTE 1—This solution is commonly referred to as a nondestructive
priate safety, health, and environmental practices and deter-
“strippingsolution”foranodiccoatings.Thissolutiondissolvestheanodic
mine the applicability of regulatory limitations prior to use.
coating with no significant attack of the substrate metal.
1.3 This international standard was developed in accor-
dance with internationally recognized principles on standard-
5. Test Specimen
ization established in the Decision on Principles for the
5.1 Prepare a test specimen of known surface area, prefer-
Development of International Standards, Guides and Recom-
ably a piece about 75 mm square. If the anodic coating is
mendations issued by the World Trade Organization Technical
contaminated or impregnated with oil, grease, lacquer, etc.,
Barriers to Trade (TBT) Committee.
remove as much as possible of this material before determining
2. Referenced Documents
the mass of the coating. It is not usually practicable to remove
these materials from the pores of the coating, but surface films
2.1 ASTM Standards:
can frequently be removed by wiping the sample with a cloth
D1193 Specification for Reagent Water
wet with a suitable solvent.
3. Significance and Use
5.2 In cases where it is required to measure the mass of
3.1 This test method is a destructive test procedure suitable
coating on only one side of a specimen where both sides have
for quality control within manufacturing operations for coating
anodic coatings, the following procedure may be used:
mass on anodically coated aluminum and aluminum alloys.
5.2.1 Prepare a specimen somewhat larger than required for
The mass of the coating is an approximation of its thickness
5.1.
provided the conditions under which the coating was applied,
5.2.2 Apply a suitable stop off around the edges of the
or the density of the coating, are known. An anodic coating’s
specimen so that the area on the side of the specimen that is not
protective value and amenability to coloring by dying or
to be tested is about 75 mm square. Paraffin wax has been used
electrolytic methods are related to mass of coating per unit
for this purpose, but any stop off that resists warm sodium
area.
hydroxide is suitable.
5.2.3 Swab the area with a warm solution of sodium
This test method is under the jurisdiction ofASTM Committee B08 on Metallic
hydroxide (10 mass %, 100 g/L) until bare metal is exposed,
and Inorganic Coatingsand is the direct respons
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