ASTM D3456-86(2008)
(Practice)Standard Practice for Determining by Exterior Exposure Tests the Susceptibility of Paint Films to Microbiological Attack
Standard Practice for Determining by Exterior Exposure Tests the Susceptibility of Paint Films to Microbiological Attack
SIGNIFICANCE AND USE
The growth of fungi and algae in and on the surface of paint films represents a major cause of discoloration or disfigurement of painted surfaces. This practice covers the preparation of coatings for testing, their application on substrates, and the arrangement of the coated panels on exterior test fences to determine the degree of microbiological attack that may occur on the surface of the coatings over a period of time. This practice is intended to provide guidelines for, and a discussion of, the various factors critical in selection of exterior coatings resistant to discoloration or disfigurement by algae and fungi.
SCOPE
1.1 This practice provides guidelines for determining the susceptibility of paint films to microbiological attack on exterior exposure. While it is recognized that various organisms may occur on an exposed coating, the specific types of organisms are mainly of academic interest. The degree to which microbiological discoloration occurs is the primary concern.
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.
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Standards Content (Sample)
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Designation: D3456 − 86 (Reapproved2008)
Standard Practice for
Determining by Exterior Exposure Tests the Susceptibility
of Paint Films to Microbiological Attack
This standard is issued under the fixed designation D3456; 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 nized that there are critical factors that influence the amount of
fungal growth that may occur on the same coated object when
1.1 This practice provides guidelines for determining the
exposed to other conditions. These factors include the geo-
susceptibility of paint films to microbiological attack on
graphic location, local atmospheric conditions such as the dust
exterior exposure. While it is recognized that various organ-
and pollen content of the air, angle of exposure, degree to
isms may occur on an exposed coating, the specific types of
which the coating is subjected to weathering, effects of
organisms are mainly of academic interest. The degree to
moisture and sunlight, the substrates on which the coating is
which microbiological discoloration occurs is the primary
applied, and the coatings in the paint system under test. The
concern.
latterfactorincludesthestabilityofthecoatingwhilepackaged
1.2 The values stated in SI units are to be regarded as the
in the container, as well as the composition of the coatings
standard. The values given in parentheses are for information
included in the total system and the thickness of each coating
only.
applied. Thus, while microorganisms occur on the surface of
1.3 This standard does not purport to address all of the
the last film applied, the degree of microbiological growth that
safety concerns, if any, associated with its use. It is the will occur is also influenced by the composition of the
responsibility of the user of this standard to establish appro-
undercoats. All the above factors should be considered in the
priate safety and health practices and determine the applica- selection of a coating resistant to discoloration by microorgan-
bility of regulatory limitations prior to use.
isms.
4. Significance and Use
2. Referenced Documents
4.1 The growth of fungi and algae in and on the surface of
2.1 ASTM Standards:
paint films represents a major cause of discoloration or
D1006 Practice for Conducting Exterior Exposure Tests of
disfigurement of painted surfaces. This practice covers the
Paints on Wood
preparation of coatings for testing, their application on
D1849 Test Method for Package Stability of Paint
substrates,andthearrangementofthecoatedpanelsonexterior
D3274 Test Method for Evaluating Degree of Surface Dis-
test fences to determine the degree of microbiological attack
figurement of Paint Films by Fungal or Algal Growth, or
that may occur on the surface of the coatings over a period of
Soil and Dirt Accumulation
time. This practice is intended to provide guidelines for, and a
3. Summary of Practice
discussionof,thevariousfactorscriticalinselectionofexterior
coatings resistant to discoloration or disfigurement by algae
3.1 Simple observation of a coated object subjected to
and fungi.
exterior exposure is considered a practical and reliable method
for determining the degree that microorganisms discolor the
5. Preparation and Application of Coatings
coating. However, this applies to a specific coated object
5.1 Conditioning of Coatings Prior to Application
exposed under a given set of conditions. It should be recog-
—Individual coatings to be used in the paint system should be
properly aged under suitable conditions prior to testing.
This practice is under the jurisdiction of ASTM Committee D01 on Paint and
Hydrolysis, amalgamation, absorption, and other physical and
Related Coatings, Materials, and Applications and is the direct responsibility of
chemical changes that may have a profound influence on the
Subcommittee D01.28 on Biodeterioration.
resistance of a coating to microorganisms usually increase with
Current edition approved June 1, 2008. Published June 2008. Originally
increasing temperature. It is recognized that actual storage
approved in 1975. Last previous edition approved in 2002 as D3456 – 86 (2002).
DOI: 10.1520/D3456-86R08.
periods of paints prior to use may vary from one to several
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
years, and the peak temperature encountered may be as warm
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
as 70°C (160°F). However, a recommended conditioning
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. period consists of 1 year at room temperatures or 1 month at
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3456 − 86 (2008)
50°C (125°F) as in Test Method D1849. The conditioning of tended use of the coatings. In referee cases, the substrate for
coatings prior to testing shall be agreeable to the producer and testingshallbemutuallyagreeabletotheproducerandtheuser.
the user in the case of a referee test.
Industrial coatings should be evaluated on the surface for
which they are designed. Trade sales and industrial mainte-
5.2 Preparation of Coatings for Application—Prior to ap-
nance coatings are general-purpose coatings and should per-
plicationofthevariouscoatingstobeincludedinthetotalpaint
form on a variety of substrates. For such coatings, test
system, thoroughly reconstitute each coating by appropriate
exposures on the following substrates are recommended for the
mixing or shaking.At the time of application, there must be no
indicated reasons.
settling, incompatibility, or other stability problem observable
in the coating in the container.
6.2 Wood Substrates—Sapwood of pine and fir generally is
considered conducive to growth of microorganisms. This may
5.3 Application of Paint System—Apply each coating in the
be due to nutrients in the wood and to the low dimensional
total paint system in an appropriate manner to provide a
stability, resulting in microcracking of coatings applied on the
specified and reasonably uniform film thickness. The presence
wood with subsequent mold growth in these cracks. Plywood,
and thickness of different coatings in the complete system can
hardboard, and other wood-derived products support varying
have a pronounced effect on the degree of microbiological
degrees of fungal growth depending on the nutrient value,
discoloration that will occur. Thus, each paint in the system
degree of moisture absorption, and dimensional stability of the
must be applied as recommended by the manufacturer. It is
base material. Redwood tends to have better dimensional
important that the procedure and the user agree on the type of
stability and otherwise has insignificant effect on the micro-
coatings and the spreading rate of each coating in the final test
biological growth on coatings applied over it. Cedar lumber
film. The drying time between coats and the curing time of the
generally contains compounds that aid in resisting microbio-
total system prior to exposure should also be specified.
Recommended practice for house paint is 2 days between coats logical growth. Both cedar and redwood contain colored
extractives that can bleed through coatings to discolor the
and no less than 7 days and not longer than 1 month prior to the
exterior exposure. Industrial and industrial maintenance coat- surface. Some of these extractives can also be nutrients that
ings may require a different practice that should be acceptable contribute to microbiological growth, resulting in added dis-
to the producer and the user. coloration.
5.4 . On each substrate use a test area not less than 310 cm
6.3 Metal Substrates—Iron, galvanized steel, and aluminum
(48 in. ) in size.When only one type of substrate is being used,
are common substrates for paints. Iron and zinc compounds
expose at least duplicate panels. When more than one substrate
generally inhibit microbiological growth. On the other hand,
is employed for each exposure condition, duplicate panels of
thesemetalsmayreactwithcertainmicrobiocidestoreducethe
each substrate are not usually required. In case of a referee test,
microbiological inhibition. Certain microbiocides can also
it is recommended that replication and size of test area be
cause discolored corrosion products or loss of adhesion by the
agreedonbetweentheproducerandtheuser.Commonpractice
coating on these surfaces.Aluminum is rather chemically inert
in the industry is to use 152 by 915-mm (6 in. (nominal) by
and does not itself promote microbiological growth. It may,
36-in.) panels for house paint exposures and to use 305-mm
however, cause loss of microbiological resistance of coatings
(12-in.) metal panels of various widths for exposures of
containing certain mercury compounds because of the amalga-
industrial and industrial maintenance coatings.
mation reacti
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