ASTM D2967-07(2017)

Standard Test Method for Corner Coverage of Powder Coatings

SIGNIFICANCE AND USE
4.1 This test method measures the degree to which different coating powder materials cover sharp corners. Corner coverage is influenced by face thickness, thixotropy, melt viscosity, surface tension, cure rate, and temperature of application and curing.
SCOPE
1.1 This test method covers the determination of the ratio of corner thickness (see 3.1.3) to face thickness (see 3.1.4) of powder coatings applied to a specific face thickness by dipping preheated square bars into aerated powder and curing the coating using predetermined conditions.
Note 1: The property of corner coverage has also been referred to as “edge coverage,” though the latter is not recommended. There are widespread misunderstandings and expectations relative to the term “edge coverage.” This test is performed on a steel bar having square corners and the results do not necessarily relate to edges that are sharper, that is, burrs. A coating that has measurable corner coverage may still not protect sharper edges from corrosion or provide the electrical insulation needed in some applications.  
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 and health 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: 31-May-2017
• ICS: 29.035.99 - Other insulating materials
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.51 - Powder Coatings

Relations

• Replaces: ASTM D2967-07(2013) - Standard Test Method for Corner Coverage of Powder Coatings
• Effective Date: 01-Jun-2017
• Refers: ASTM D374/D374M-23 - Standard Test Methods for Thickness of Solid Electrical Insulation
• Effective Date: 01-Oct-2023
• Referred By: ASTM D3451-06(2017) - Standard Guide for Testing Coating Powders and Powder Coatings
• Effective Date: 01-Jun-2017
• Referred By: ASTM D1711-22 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Jun-2017
• Referred By: ASTM D4242-07(2017) - Standard Test Method for Inclined Plate Flow for Thermosetting Coating Powders
• Effective Date: 01-Jun-2017
• Referred By: ASTM D3963/D3963M-21 - Standard Specification for Fabrication and Jobsite Handling of Epoxy-Coated Steel Reinforcing Bars
• Effective Date: 01-Jun-2017
• Referred By: ASTM A1124/A1124M-23 - Standard Specification for Textured Epoxy-Coated Steel Reinforcing Bars
• Effective Date: 01-Jun-2017
• Referred By: ASTM A775/A775M-22 - Standard Specification for Epoxy-Coated Steel Reinforcing Bars
• Effective Date: 01-Jun-2017

Overview

ASTM D2967-07(2017), "Standard Test Method for Corner Coverage of Powder Coatings," is an internationally recognized procedure published by ASTM International. This standard outlines a method for evaluating how well powder coating materials cover the sharp corners of steel substrates. The primary aim is to measure the ratio of powder coating thickness at corners compared to flat surfaces, providing vital insights into material behavior and coating performance in challenging geometric features.

Corner coverage is a crucial factor affecting the protective and decorative properties of powder coatings, particularly in industrial, automotive, and architectural applications where sharp edges are common. The results support powder coating manufacturers, users, and quality assurance professionals in comparing products and confirming conformance to performance requirements.

Key Topics

• Corner Coverage Ratio: Assesses the relationship between coating thickness at a 90° corner and on the adjacent flat faces.
• Test Specimens and Procedure:
  • Involves coating preheated steel bars with aerated powder and curing under set conditions.
  • Measurements include distances across flat surfaces and diagonals to calculate face and corner thickness.
• Material Properties Influencing Results:
  • Thixotropy
  • Melt viscosity
  • Surface tension
  • Cure rate
  • Application and curing temperature
• Precision and Bias: The method standardizes results for direct and reliable comparison, with precision considered adequate within single laboratories for higher coverage values.
• Terminology Clarification:
  • Refers to ‘corner coverage’ rather than ‘edge coverage’, as the latter term can be misunderstood, especially in relation to extremely sharp or burred edges.

Applications

The ASTM D2967-07(2017) test method has broad applications across sectors involving powder coatings:

• Quality Control and R&D: Enables comparative analysis of different powder coating formulations for reliable edge protection and finish consistency.
• Product Specification Compliance: Helps ensure that powder-coated products meet durability and performance criteria, especially where sharp-edged substrates are common.
• Industrial Manufacturing: Assists manufacturers in process optimization, particularly in sectors such as automotive, appliances, furniture, and architectural metals where edge coverage impacts product lifespan and appearance.
• Corrosion Protection and Electrical Insulation: While valuable for evaluation, the standard notes its results for corner coverage may not fully predict protection on sharper edges or meet stringent insulation needs in certain cases.

Related Standards

• ASTM D374/D374M: Test Methods for Thickness of Solid Electrical Insulation, referenced for measurement procedures.
• Powder Coating Standards: Other ASTM standards covering powder application, curing, and performance evaluation may complement this method in a comprehensive testing program.
• International Principles: Developed in accordance with World Trade Organization (WTO) principles for international standardization, supporting global trade and regulatory compliance.

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Keywords: ASTM D2967-07, powder coating, corner coverage, coating thickness, powder coatings test method, quality control, industrial coatings, edge protection, powder coating standards, ASTM International

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: D2967 − 07 (Reapproved 2017)
Standard Test Method for
Corner Coverage of Powder Coatings
This standard is issued under the fixed designation D2967; 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. Terminology
1.1 This test method covers the determination of the ratio of 3.1 Definitions:
3.1.1 coating powders, n—finely divided particles of resin,
corner thickness (see 3.1.3) to face thickness (see 3.1.4)of
either thermoplastic or thermosetting, generally incorporating
powder coatings applied to a specific face thickness by dipping
pigments, fillers, and additives and remaining finely divided
preheated square bars into aerated powder and curing the
during storage under suitable conditions, which, after fusing
coating using predetermined conditions.
and possibly curing, give a continuous film.
NOTE 1—The property of corner coverage has also been referred to as
3.1.1.1 Discussion—The coating powder may contain
“edge coverage,” though the latter is not recommended. There are
fillers, colorants, curing agents, etc., consistent with producing
widespread misunderstandings and expectations relative to the term “edge
thedesiredcoatings.Thepowderisappliedbyvariousmethods
coverage.” This test is performed on a steel bar having square corners and
the results do not necessarily relate to edges that are sharper, that is, burrs.
such as spraying, sprinkling, or dipping. Usually hot parts are
A coating that has measurable corner coverage may still not protect
used. Heat causes the powder to melt and flow into a dense
sharper edges from corrosion or provide the electrical insulation needed in
coating.
some applications.
3.1.2 corner coverage, n—of powder coating, the ratio of
1.2 The values stated in SI units are to be regarded as the
the corner thickness to the face thickness of the fused coating
standard. The values given in parentheses are for information
expressed in percent.
only.
3.1.3 corner thickness, n—of powder coating, the average
1.3 This standard does not purport to address all of the
thickness of the coating on sharp 90° corners of steel bars
safety concerns, if any, associated with its use. It is the
measured at 45° to the flat surfaces.
responsibility of the user of this standard to establish appro-
3.1.4 face thickness, n—of powder coating, the average
priate safety and health practices and determine the applica-
thickness of the coating on flat surfaces of steel bars measured
bility of regulatory limitations prior to use.
perpendicular to the surfaces.
1.4 This international standard was developed in accor-
3.1.5 powder coatings, n—coatings which are protective or
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the decorative, or both, formed by the application of a coating
powder to a substrate and fused in a continuous film by the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical application of heat or radiant energy.
Barriers to Trade (TBT) Committee.
4. Significance and Use
4.1 This test method measures the degree to which different
2. Referenced Documents
coating powder materials cover sharp corners. Corner coverage
2.1 ASTM Standards:
is influenced by face thickness, thixotropy, melt viscosity,
D374/D374M Test Methods for Thickness of Solid Electri-
surface tension, cure rate, and temperature of application and
cal Insulation
curing.
5. Apparatus
This test method is under the jurisdiction of ASTM Committee D01 on Paint
5.1 Aerated Bed—Suitable for providing a uniformly sus-
and Related Coatings, Materials, andApplications and is the direct responsibility of
pended dense phase of free–moving powder. Fig. 1 shows a
Subcommittee D01.51 on Powder Coatings.
schematic of an aerated bed used for suspending the coating
Current edition approved June 1, 2017. Published June 2017. Originally
powder.The equipment consists of an open top chamber which
approved in 1971. Last previous edition approved in 2013 as D2967 – 07 (2013).
DOI: 10.1520/D2967-07R17.
has a porous plate for a false bottom. Air is introduced under
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the plate at a low pressure so that it filters through the porous
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
plate and uniformly suspends the particles contained in the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. chamber.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2967 − 07 (2017)
removalincludetheuseofstrippingsolutions,heat,andcareful
scraping with a sharp blade, or combinations thereof.
6. Sampling
6.1 The powder sample shall be from one lot and be
representative of the lot.
7. Test Specimens
7.1 The test specimens shall be the steel ba
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