ASTM D6900-10(2020)

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: D6900 − 10 (Reapproved 2020)
Standard Test Method for
Wet Adhesion of Latex Paints to a Gloss Alkyd Enamel
Substrate
This standard is issued under the fixed designation D6900; 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 a procedure for measuring by 3.1 Definitions of Terms Specific to This Standard:
scrubbing the adhesion of latex paints to glossy alkyd enamel
3.1.1 wet adhesion, n—the ability of a coating to resist
substrates after exposure to wet conditions.
removal by scrubbing from the surface beneath it after expo-
sure to wet conditions and abrasion.
1.2 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
4. Summary of Test Method
only.
4.1 Test paints, with optional control paint, are drawn down
1.3 This standard does not purport to address all of the
using a 7-mil clearance Dow applicator (~11 m /L) across a
safety concerns, if any, associated with its use. It is the
cured alkyd gloss enamel previously drawn down on a black or
responsibility of the user of this standard to establish appro-
white plastic panel.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4.2 The drawdown films are allowed to dry under standard-
1.4 This international standard was developed in accor-
izedconditions.Then,eighteencutsaremadetoforma6by10
dance with internationally recognized principles on standard-
cut block, creating sixty 6.4 mm (0.25 in) squares, in the center
ization established in the Decision on Principles for the
of each film with a razor blade.
Development of International Standards, Guides and Recom-
4.3 The panels are then soaked for 30 min in ambient tap
mendations issued by the World Trade Organization Technical
water. The panel is mounted in a washability tester and 20 mL
Barriers to Trade (TBT) Committee.
of water are applied. The panel is then scrubbed for up to 500
cycles or until all of the squares within each block are
2. Referenced Documents
2 completely removed.
2.1 ASTM Standards:
D523 Test Method for Specular Gloss
5. Significance and Use
D714 Test Method for Evaluating Degree of Blistering of
Paints
5.1 After application to either interior or exterior surfaces,
D2486 Test Methods for Scrub Resistance of Wall Paints
latex paints may be subjected to conditions of high humidity,
D3924 Specification for Standard Environment for Condi- condensation, or precipitation. This may sometimes lead to a
tioning and Testing Paint, Varnish, Lacquer, and Related
loss of adhesion to the substrate over which they have been
Materials applied. This method is a quantitative measure of the adhesion
E691 Practice for Conducting an Interlaboratory Study to
of latex paints to glossy substrates under such conditions.
Determine the Precision of a Test Method
E177 Practice for Use of the Terms Precision and Bias in
6. Apparatus
ASTM Test Methods
6.1 Constanttemperature/humidityroominaccordancewith
Specification D3924 [23 6 2°C (73.5 6 3.5°F) and 50 65%
1 relative humidity].
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
6.2 Drawdown Plate.
Subcommittee D01.42 on Architectural Coatings.
Current edition approved Dec. 1, 2020. Published December 2020. Originally
6.3 Straight Line Washability Tester and Accessories, per
approved in 2003. Last previous edition approved in 2015 as D6900 – 10 (2015).
Test Methods D2486.
DOI:10.1520/D6900-10R20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.4 Nylon Bristle Brush and Accessories (nominal weight
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
455 g), having nylon brush bristles in 5/4 pattern extending 19
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. mm ( ⁄4 in.) from block (as per Test Methods D2486).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6900 − 10 (2020)
6.5 Dow FilmApplicator,having7-mil(0.18-mm)clearance 8.2.2 Condition the panels for one week in the constant
by 5.2-in. (132-mm) width. applicator blade. temperature/humidity room as specified in Specification
D3924 or under other conditions agreed upon by buyer and
6.6 Single-edge Razor Blade, in safety holder.
seller.Shorterconditioningtimesmaybeusedifmorestringent
6.7 Metal Straight Edge (or appropriate guide).
measures of wet adhesion are needed, as in the case of
determining a coating’s “early” wet adhesion.
7. Reagents and Materials
NOTE 2—Since humidity and temperature both markedly influence the
7.1 A ready-mix deep-tint alkyd gloss enamel with a 60°
rateatwhichpaintdries,aconstanttemperature/humidityroomisstrongly
gloss of at least 65 as measured in accordance with Test
recommended in order to achieve reproducible results using this method.
Method D523 (or alkyd as agreed upon by the purchaser and
8.2.3 Condition, break in and rinse the scrub brush as
supplier).
specified in Test Methods D2486.
7.2 Plastic test panels as used in Test Methods D2486.
8.2.4 Using a metal straightedge or suitable guide, make
eighteen razor blade cuts, spaced 6.4 mm (0.25 in.) apart
8. Procedure
forminga6by10 array with a razor blade in the center of each
8.1 Preparation of the Alkyd Substrate Panels—Attach the paint (See Fig. 1.). Each cut should be made in one steady
motion with sufficient pressure to cut, but not tear the latex
plastic panel to the drawdown plate and drawdown the alkyd
gloss enamel lengthwise using a 7-mil clearance Dow appli- paint film. (Warning—Avoid cutting completely through the
alkyd enamel into the plastic substrate.)
cator. The time for application should be fairly slow—3 to 4 s
from end to end. The drawdown must be free of ridges, 8.2.5 Submerge each panel face-up for 30 min in a flat
container of ambient tap water, being careful not to bend the
holidays, specks, or other imperfections, which may affect
adhesion. substrate.
8.2.6 Removethepanelfromthewaterandquicklyexamine
8.1.1 Allow the alkyd gloss enamel to air-dry in a horizontal
position.Allowtocuretypicallyforaminimumofthreeweeks. the panel for blistering, per Test Method D714 (optional).
Immediatelysecurethepanelinthewashabilitytesterusingthe
Panels are to be used between three to six weeks from the date
of preparation. Wet adhesion with some latex paints may be gasketed frame accessory, ensuring that the array is in the path
of the brush. Place 20 mLof water in the path of the brush and
dramatically reduced if the alkyd is allowed to cure for more
than six weeks.
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