ASTM D6944-15(2020)

Standard Practice for Determining the Resistance of Cured Coatings to Thermal Cycling

SIGNIFICANCE AND USE
4.1 The purpose of this test is to obtain information on the ability of a coating system to adhere to substrates under thermal stress. It is assumed that the coating systems tested are applied and cured according to the coating manufacturer’s instructions.
SCOPE
1.1 This practice determines the resistance of cured coatings or coating systems to repeated thermal cycles and is designed to assess the effect of thermal cycling on the properties of a coating or coating system. These properties may include adhesion, resistance to checking, cracking, blistering, or others. This procedure is not intended to provide a quantitative measure of the service life that can be expected from a specific coating system on a given substrate.  
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.

General Information

• Status: Published
• Publication Date: 31-Jan-2020
• ICS: 87.040 - Paints and varnishes
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.46 - Industrial Protective Coatings

Relations

• Replaces: ASTM D6944-15 - Standard Practice for Determining the Resistance of Cured Coatings to Thermal Cycling
• Effective Date: 01-Feb-2020
• Refers: ASTM D660-93(2019) - Standard Test Method for Evaluating Degree of Checking of Exterior Paints
• Effective Date: 01-Oct-2019
• Refers: ASTM D661-93(2019) - Standard Test Method for Evaluating Degree of Cracking of Exterior Paints
• Effective Date: 01-Oct-2019
• Refers: ASTM G147-17 - Standard Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering Tests
• Effective Date: 01-Jun-2017
• Refers: ASTM D6132-13 - Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Coating Thickness Gage
• Effective Date: 01-Nov-2013
• Refers: ASTM D6677-07(2012) - Standard Test Method for Evaluating Adhesion by Knife
• Effective Date: 01-Nov-2012
• Refers: ASTM D7234-12 - Standard Test Method for Pull-Off Adhesion Strength of Coatings on Concrete Using Portable Pull-Off Adhesion Testers
• Effective Date: 01-Jul-2012
• Refers: ASTM D7091-12 - Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals
• Effective Date: 01-Apr-2012
• Refers: ASTM D661-93(2011) - Standard Test Method for Evaluating Degree of Cracking of Exterior Paints
• Effective Date: 01-Nov-2011
• Refers: ASTM D660-93(2011) - Standard Test Method for Evaluating Degree of Checking of Exterior Paints
• Effective Date: 01-Nov-2011
• Refers: ASTM D714-02(2009) - Standard Test Method for Evaluating Degree of Blistering of Paints
• Effective Date: 01-Jul-2009
• Refers: ASTM D3359-09e1 - Standard Test Methods for Measuring Adhesion by Tape Test
• Effective Date: 01-Jun-2009
• Refers: ASTM G147-09 - Standard Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering Tests
• Effective Date: 01-Feb-2009
• Refers: ASTM D4541-09 - Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers
• Effective Date: 01-Feb-2009
• Refers: ASTM D6132-08 - Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Gage
• Effective Date: 01-Jul-2008

Overview

ASTM D6944-15(2020), Standard Practice for Determining the Resistance of Cured Coatings to Thermal Cycling, is a globally recognized method developed by ASTM International. This standard evaluates how well cured coatings and coating systems can resist damage when subjected to repeated cycles of heating, freezing, and, where applicable, immersion. By simulating exposure to thermal cycling, this practice provides valuable insight into a coating's ability to maintain adhesion and avoid deterioration such as cracking, blistering, or checking under thermal stress.

This standard does not give a quantitative prediction of a coating's service life but is widely used for comparative analysis and qualification in laboratory environments, following international standards principles established by the World Trade Organization (WTO) Technical Barriers to Trade (TBT) Committee.

Key Topics

• Thermal Cycling of Coatings: Outlines procedures to subject cured coatings to repeated cycles of high and low temperatures, with optional immersion, to simulate real-world environmental stress.
• Adhesion and Integrity Assessment: Focuses on evaluating changes in adhesion, as well as the degree of checking, cracking, and blistering, giving users a clear understanding of coating integrity after thermal cycling.
• Test Methods:
  • Test Method A: Combines cycles of heating, freezing, and immersion.
  • Test Method B: Involves cycles of heating and freezing only.
• Test Specimens: Requires specimens prepared according to agreed upon substrate types, surface conditions, and coating thickness. Control specimens are recommended for reliable comparison.
• Reporting and Evaluation: Results are reported after cycling, including adhesion values, visual assessments, and specimen descriptions, ensuring traceability and repeatability.
• Safety and Environmental Considerations: The standard mandates that all users assess and comply with relevant safety and environmental practices.

Applications

ASTM D6944-15(2020) is crucial for industries where coating durability under thermal stress is essential. Typical applications include:

• Protective Coatings for Infrastructure: Evaluating paints and coatings applied to steel, concrete, and other construction materials for bridges, tanks, pipelines, and buildings.
• Industrial Equipment: Verifying coating performance on machinery and equipment exposed to temperature fluctuations.
• Transport and Automotive: Testing coatings on vehicle parts, rail systems, and aerospace components to ensure resilience against temperature extremes.
• Research and Development: Used in laboratories for comparative testing of new or modified coating formulations and to qualify products before launch.
• Quality Control and Certification: Integral to product validation, project specifications, and regulatory compliance in both manufacturing and construction sectors.

By following this standard, stakeholders can select and qualify coating systems that meet the demands of environments with significant temperature shifts, reducing the risk of coating failure and associated maintenance costs.

Related Standards

The following standards are often referenced alongside ASTM D6944-15(2020) to enhance the assessment of coatings under thermal cycling:

• ASTM D660: Test Method for Evaluating Degree of Checking of Exterior Paints
• ASTM D661: Test Method for Evaluating Degree of Cracking of Exterior Paints
• ASTM D714: Test Method for Evaluating Degree of Blistering of Paints
• ASTM D3359: Test Methods for Rating Adhesion by Tape Test
• ASTM D4541: Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers
• ASTM D6677: Test Method for Evaluating Adhesion by Knife
• ASTM D7091: Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings
• ASTM D6132: Test Method for Nondestructive Measurement of Dry Film Thickness with Ultrasonic Gage
• ASTM G147: Practice for Conditioning and Handling of Nonmetallic Materials for Weathering Tests

Implementing ASTM D6944-15(2020) alongside these standards ensures a comprehensive assessment of coating systems, supporting optimal product performance and reliability in thermally challenging environments.

Standards Content (Sample)

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: D6944 − 15 (Reapproved 2020)
Standard Practice for
Determining the Resistance of Cured Coatings to Thermal
Cycling
This standard is issued under the fixed designation D6944; 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.
1. Scope D6132 Test Method for Nondestructive Measurement of Dry
Film Thickness of Applied Organic Coatings Using an
1.1 Thispracticedeterminestheresistanceofcuredcoatings
Ultrasonic Coating Thickness Gage
or coating systems to repeated thermal cycles and is designed
D6677 Test Method for Evaluating Adhesion by Knife
to assess the effect of thermal cycling on the properties of a
D7091 Practice for Nondestructive Measurement of Dry
coating or coating system. These properties may include
Film Thickness of Nonmagnetic Coatings Applied to
adhesion,resistancetochecking,cracking,blistering,orothers.
Ferrous Metals and Nonmagnetic, Nonconductive Coat-
This procedure is not intended to provide a quantitative
ings Applied to Non-Ferrous Metals
measure of the service life that can be expected from a specific
D7234 Test Method for Pull-OffAdhesion Strength of Coat-
coating system on a given substrate.
ings on Concrete Using Portable Pull-Off Adhesion Tes-
1.2 This standard does not purport to address all of the
ters
safety concerns, if any, associated with its use. It is the
G147 Practice for Conditioning and Handling of Nonmetal-
responsibility of the user of this standard to establish appro-
lic Materials for Natural and Artificial Weathering Tests
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Summary of Test Methods
1.3 This international standard was developed in accor-
3.1 Test Method A—Cured test specimens are subjected to
dance with internationally recognized principles on standard-
30 thermal cycles of immersion, freezing and heating.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3.2 Test Method B—Cured test specimens are subjected to
mendations issued by the World Trade Organization Technical 30 thermal cycles of freezing and heating.
Barriers to Trade (TBT) Committee.
4. Significance and Use
2. Referenced Documents
4.1 The purpose of this test is to obtain information on the
2.1 ASTM Standards:
ability of a coating system to adhere to substrates under
D660 Test Method for Evaluating Degree of Checking of
thermal stress. It is assumed that the coating systems tested are
Exterior Paints
applied and cured according to the coating manufacturer’s
D661 Test Method for Evaluating Degree of Cracking of
instructions.
Exterior Paints
D714 Test Method for Evaluating Degree of Blistering of
TEST METHOD A—FREEZE/THAW/IMMERSION
Paints
D3359 Test Methods for Rating Adhesion by Tape Test
5. Apparatus
D4541 Test Method for Pull-Off Strength of Coatings Using
Portable Adhesion Testers 5.1 Thermal Cycling Apparatus:
5.1.1 The thermal cycling apparatus shall consist of a
suitable chamber or chambers in which the test specimens may
This practice is under the jurisdiction of ASTM Committee D01 on Paint and
undergo the specified cycle. Ideally, a chamber which contains
Related Coatings, Materials, and Applications and is the direct responsibility of
heatingandrefrigerationequipmentandimmersioncapabilities
Subcommittee D01.46 on Industrial Protective Coatings.
in the same unit should be used. This chamber shall have the
Current edition approved Feb. 1, 2020. Published February 2020. Originally
ability to maintain continuous reproducible cycles within the
approved in 2003. Last previous edition approved in 2015 as D6944 – 15. DOI:
10.1520/D6944-15R20.
specified temperature requirements. In the event that an appa-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ratus having freezing, heating, and immersion capabilities is
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
not available, separate equipment for freezing, heating and
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. immersion may be used.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6944 − 15 (2020)
5.1.2 The chamber or chambers shall have the ability to
Condition Time (h)
50±3°C(122±5°F)inair 4
maintain a constant temperature during each of the respective
25 ± 3°C (77 ± 5°F) tap water immersion 4
temperature intervals as specified by the procedure.
-29 ± 3°C (–20 ± 5°F) in air 16
5.1.3 The samples shall be arranged to minimize contact
7.2 Repeat this cycle of heat/immersion/freeze for 30
with the chamber surfaces or any mounting racks, and to
cycles, or other agreed upon number of cycles. Leave the
maximize air flow.
surfaceofthepanelswetwhentransferringfromtheimmersion
5.1.4 The temperature of the thermal cycling apparatus shall
to the freeze cycle. Maintain panels in the freeze condition
give uniform readings at various locations within the chamber,
upon interruptions in the cycling (for example, weekends/
within 3°C (5°F) at any given time, except during the transition
holidays). Evaluate specimens either every 5 cycles or at the
between heating and freezing cycles. A two hour temperature
end of 30 cycles. Destructive tests are typically performed at
rampingperiodispermittedfortheequipmenttoreachthenext
the completion of all cycles.
temperature setting.
TEST METHOD B—FREEZE/THAW
6. Test Specimens
8. Apparatus
6.1 Apply each coating or coating system onto the substrate
type and thickness as agreed upon. Preparation of the substrate
8.1 Thermal Cycling Apparatus:
(that is, surface cleanliness and roughness) prior to application
8.1.1 The thermal cycling appa
...