ASTM D6441-05

Standard Test Methods for Measuring the Hiding Power of Powder Coatings

SIGNIFICANCE AND USE
Contrast ratio at a specified film thickness is a useful hiding power parameter for production control and purchasing specifications.
The greater the hiding power, the less coating is required per unit area to obtain adequate hiding. Knowledge of hiding power is therefore important in regard to coating costs and for comparing coating value.
SCOPE
1.1 These test methods determine and report the hiding power of a powder coating with respect to two parameters:
1.1.1 Test Method A-Contrast Ratio at a given film thickness
1.1.2 Test Method B-Film thickness at 0.98 (98%) contrast ratio.
Note 1-The measured parameters conform to powder coating industry practice by measuring hiding power in relation to film thickness, rather than the more conventional "Spreading Rate" function employed in Test Methods D 344 and D 2805 and other hiding power test methods.
Note 2-Hiding power is photometrically defined as the spreading rate at 0.98 contrast ratio. See definitions of spreading rate and hiding power in Terminology D 16, D 2805, and the Paint and Coatings Testing Manual.
Note 3-The contrast ratio of 0.98 is conventionally accepted in the coatings industry as representing "complete" hiding for reflectometric hiding power measurements. But visually, as well as photometrically, it is slightly less than complete.
1.2 These test methods cover the determination of the hiding power of powder coatings applied by electrostatic spraying.
1.3 These test methods determine hiding power by means of reflectometric and thickness gage measurements. They are limited to coatings having a minimum CIE-Y reflectance of 15 %.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 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.

General Information

• Status: Historical
• Publication Date: 31-Dec-2004
• ICS: 87.040 - Paints and varnishes
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.51 - Powder Coatings

Relations

• Replaces: ASTM D6441-99ae1 - Standard Test Methods for Measuring the Hiding Power of Powder Coatings
• Effective Date: 01-Jan-2005
• Replaced By: ASTM D6441-05(2010) - Standard Test Methods for Measuring the Hiding Power of Powder Coatings
• Effective Date: 01-Dec-2010
• Referred By: ASTM D3451-06(2017) - Standard Guide for Testing Coating Powders and Powder Coatings
• Effective Date: 01-Jan-2005

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D6441–05
Standard Test Methods for
1
Measuring the Hiding Power of Powder Coatings
This standard is issued under the fixed designation D6441; 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 2. Referenced Documents
2
1.1 These test methods determine and report the hiding 2.1 ASTM Standards:
power of a powder coating with respect to two parameters: D16 Terminology for Paint, Related Coatings, Materials,
1.1.1 Test Method A—Contrast Ratio at a given film thick- and Applications
ness D344 Test Method for Relative Hiding Power of Paints by
1.1.2 Test Method B—Film thickness at 0.98 (98 %) con- the Visual Evaluation of Brushouts
trast ratio. D2805 Test Method for Hiding Power of Paints by Reflec-
tometry
NOTE 1—The measured parameters follow powder coating industry
D3451 Guide for Testing Coating Powders and Powder
practice by measuring hiding power in relation to film thickness, rather
Coatings
than the “Spreading Rate” function employed in Test Methods D344 and
D2805 and other hiding power test methods. E284 Terminology of Appearance
NOTE 2—Hiding power is photometrically defined as the spreading rate
E1331 Test Method for Reflectance Factor and Color by
at 0.98 contrast ratio. See definitions of spreading rate and hiding power
Spectrophotometry Using Hemispherical Geometry
in Terminology D16, D2805, and the Paint and Coatings Testing Manual.
E1347 Test Method for Color and Color-Difference Mea-
NOTE 3—The contrast ratio 0.98 is conventionally accepted in the
surement by Tristimulus Colorimetry
coatings industry as representing “complete” hiding for reflectometric
E1349 Test Method for Reflectance Factor and Color by
hiding power measurements. But visually, as well as photometrically, it is
Spectrophotometry Using Bidirectional (45°:0° or 0°:45°)
slightly less than complete.
Geometry
1.2 These test methods cover the determination of the
2.2 Other Standard:
hiding power of powder coatings applied by electrostatic
1-GP-71 Method 14.7, Hiding Power, Contrast Ratio
spraying.
3
Method, October 1982
1.3 Thesetestmethodsdeterminehidingpowerbymeansof
reflectometric and thickness gage measurements. They are
3. Terminology
limited to coatings having a minimum CIE-Y reflectance of
3.1 Definitions of Terms Specific to This Standard:
15 %.
3.1.1 reflectance—term of wide applicability, referring
1.4 The values stated in SI units are to be regarded as the
herein to the luminous reflectance factor as defined in Termi-
standard. The values given in parentheses are for information
nology E284, and equivalent to the CIE Tristimulus value Y
only.
measured in accordance with Test Methods E1331, E1347 or
1.5 This standard does not purport to address all of the
Test Method E1349 with specular reflection excluded. It is
safety concerns, if any, associated with its use. It is the
expressed as a percentage in this standard.
responsibility of the user of this standard to establish appro-
3.1.2 white substrate—For purposes of this test, a substrate
priate safety and health practices, and to determine in advance
of neutral shade with a minimum reflectance of 78 %.
the applicability of regulatory limitations prior to use.
1 2
These test methods are under the jurisdiction of ASTM Committee D01 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
PaintandRelatedCoatings,Materials,andApplicationsandthedirectresponsibility contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
of Subcommittee D01.51 on Powder Coatings. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2005. Published February 2005. Originally the ASTM website.
´1 3
approved in 1999. Last previous edition approved in 1999 as D6441 – 99a . DOI: Canadian General Standards Board, (CGSB), 222 Queen St., Ottawa, Ont.,
10.1520/D6441-05. Canada K1A 1G6.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
D6441–05
NOTE 1—Shows black and white substrate areas exposed after removal of masking tape.
FIG. 1 “Wedge” Film Application
3.1.3 black substrate—A substrate with a maximum reflec- 3.1.9 wedge of coating—Afilmofcoatinghavingarangeof
tance of 1 %, which is effectively zero for the purpose of film thickness giving a corresponding range of opacities on a
measuring hiding power. black and white substrate. (see Fig. 1).
3.1.4 white reflectance (R )—Reflectance of the applied
3.2 Definitions of Symbols Used in Calculations Specific to
W
test film over a white s
...