ASTM D6491-09(2023)

Standard Practice for Evaluation of Aging Resistance of Prestressed Prepainted Metal In a Dry Heat Test

ABSTRACT
This practice details the standard procedure for evaluating the resistance of prestressed prepainted metal panels to cracking, or loss of adhesion, or both, after accelerated heat aging by dry heat test. This test method requires the use of gravity or forced air laboratory oven, bench vise, bending dies or test shims, 10x magnifier, and adhesive tape.
SCOPE
1.1 This practice can be used to evaluate the resistance of a prestressed prepainted metal panel to cracking, or loss of adhesion, or both, after accelerated heat aging. Most coil coated products are formed and bent into specific shapes to produce a final product. These operations introduce stresses, which may be relieved by cracking of the coating after aging.  
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.3 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.  
1.4 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: 28-Feb-2023
• ICS: 87.020 - Paint coating processes
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.53 - Coil Coated Metal

Relations

• Refers: ASTM D4145-10 - Standard Test Method for Coating Flexibility of Prepainted Sheet
• Effective Date: 01-Jun-2010
• Refers: ASTM D4145-83(2002) - Standard Test Method for Coating Flexibility of Prepainted Sheet
• Effective Date: 25-Mar-1983
• Refers: ASTM D4145-83(1996)e1 - Standard Test Method for Coating Flexibility of Prepainted Sheet
• Effective Date: 25-Mar-1983

Overview

ASTM D6491-09(2023) is the Standard Practice for the Evaluation of Aging Resistance of Prestressed Prepainted Metal in a Dry Heat Test. Developed by ASTM International, this standard outlines procedures to assess how prepainted metal panels withstand cracking or loss of adhesion after accelerated heat aging. Understanding the aging resistance of coil coated metals is crucial, as most products undergo shaping and bending during manufacturing, which can introduce mechanical stresses that may affect coating durability.

This standard ensures a consistent method for evaluating mechanical and adhesion failures in such coatings, providing value to manufacturers, suppliers, and quality assurance professionals dealing with coil-coated metal products.

Key Topics

• Scope and Purpose

  • Evaluates resistance to cracking and loss of coating adhesion in prestressed prepainted metals following dry heat exposure.
  • Applies to coil coated products subjected to bending or forming during manufacturing.
  • Results help identify coating systems' durability and suitability for intended uses.

• Test Apparatus

  • Gravity or forced air laboratory oven, capable of maintaining specified test temperatures.
  • Bench vise with smooth jaws or equivalent equipment to create bends in metal samples.
  • Optional: bending dies, test shims, 10x magnifier for detailed inspection.
  • Adhesive tape for adhesion testing.

• Sample Preparation & Procedure

  • Samples are cut to standardized dimensions, with the bend direction agreed upon between customer and vendor.
  • Fabrication and testing are performed at controlled room temperatures, with alternate temperatures permitted by agreement.
  • Three T-bend specimens are prepared and tested per ASTM D4145.
  • Test specimens are subjected to dry heat aging in an oven, then inspected.
  • Adhesion and cracking are evaluated both before and after aging.

• Reporting

  • Documentation includes details on substrate, coating system, production dates, test results, and any observations related to cracking and pick-off both before and after heat aging.

Applications

ASTM D6491-09(2023) has practical applications along the entire value chain of prepainted metals, including:

• Quality Control: Used in manufacturing plants to verify coating performance against cracking and adhesive loss after forming and thermal aging.
• Product Development: Enables R&D teams to compare and select coating systems that offer superior resistance to mechanical and thermal stresses.
• Supplier-Customer Agreements: Provides objective criteria for specifying and testing prepainted metals in purchase contracts, ensuring product conformity and performance.
• Failure Analysis: Assists in diagnosing coating problems in existing installations and identifying whether aging or fabrication processes are contributing factors.
• Regulatory Compliance: Fulfills customer and regulatory expectations for durability in environments where metal panels face significant temperature variations and mechanical stresses.

Relevant industries include construction, appliance manufacturing, automotive panels, and other sectors utilizing coil coated metal products.

Related Standards

• ASTM D4145: Test Method for Coating Flexibility of Prepainted Sheet, referenced for T-bend specimen preparation and evaluation.
• ASTM D01: Committee on Paint and Related Coatings, Materials, and Applications, overseeing related standards for coatings and coil coated metals.

Manufacturers and laboratories may also refer to other coatings performance and durability standards, such as those dealing with corrosion resistance, weathering, or chemical exposure, to comprehensively assess prepainted metal products.

By following ASTM D6491-09(2023), stakeholders ensure the reliability and longevity of prestressed prepainted metal products through standardized dry heat test methods, ultimately contributing to enhanced product performance and customer satisfaction.

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: D6491 − 09 (Reapproved 2023)
Standard Practice for
Evaluation of Aging Resistance of Prestressed Prepainted
Metal In a Dry Heat Test
This standard is issued under the fixed designation D6491; 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 3.2 Bench Vise, with smooth jaws or inserts, 130 mm (5 in.)
permanently mounted on a work table or bench, or alternative
1.1 This practice can be used to evaluate the resistance of a
equipment capable of making the appropriate bends.
prestressed prepainted metal panel to cracking, or loss of
3.3 Bending Dies or Test Shims, (optional).
adhesion, or both, after accelerated heat aging. Most coil
coated products are formed and bent into specific shapes to
3.4 10X magnifier, (optional).
produce a final product. These operations introduce stresses,
3.5 Adhesive Tape.
which may be relieved by cracking of the coating after aging.
1.2 The values stated in SI units are to be regarded as the 4. Test Specimens
standard. The values given in parentheses are for information
4.1 Cut samples 75 mm (3 in.) wide (across the bend
only.
direction) by whatever length is necessary to make the appro-
1.3 This standard does not purport to address all of the priate number of bends. The direction of the bend may be
transverse or longitudinal to the “rolling direction” of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- metal—or as agreed upon between customer and vendor.
priate safety, health, and environmental practices and deter-
5. Procedure
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
5.1 Perform the fabrication at room temperature, 25 °C 6
dance with internationally recognized principles on standard-
1 °C (77 °F 6 2 °F). All test specimens should be equilibrated
ization established in the Decision on Principles for the
to the same temperature before fabricating. Different fabrica-
Development of International Standards, Guides and Recom-
tion temperatures may be used, when needed, to meet customer
mendations issued by the World Trade Organization Technical
or vendor requirements, or both.
Barriers to Trade (TBT) Committee.
5.2 Prepare three “T-bend” test specimens in accordance
with Test Method D4145. The T-bend used should be agreed
2. Referenced Documents
upon between customer and vendor.
2.1 ASTM Standards:
5.3 Examine the T-bend for cracking and tape pick-off in
D4145 Test Method for Coating Flexibility of Prepainted
accordance with Test Method D4145 and record the results.
Sheet
5.4 Place the formed test specimens in the 60 °C 6 3 °C
(140 °F 6 5 °F) oven for 16 h. Different ti
...