ASTM D3456-86(1996)
(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
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 This standard does not purport to address all of the safety problems, 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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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: D 3456 – 86 (Reapproved 1996)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Determining by Exterior Exposure Tests the Susceptibility
of Paint Films to Microbiological Attack
This standard is issued under the fixed designation D 3456; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope latter factor includes the stability of the coating while packaged
in the container, as well as the composition of the coatings
1.1 This practice provides guidelines for determining the
included in the total system and the thickness of each coating
susceptibility of paint films to microbiological attack on
applied. Thus, while microorganisms occur on the surface of
exterior exposure. While it is recognized that various organ-
the last film applied, the degree of microbiological growth that
isms may occur on an exposed coating, the specific types of
will occur is also influenced by the composition of the
organisms are mainly of academic interest. The degree to
undercoats. All the above factors should be considered in the
which microbiological discoloration occurs is the primary
selection of a coating resistant to discoloration by microorgan-
concern.
isms.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 The growth of fungi and algae in and on the surface of
priate safety and health practices and determine the applica-
paint films represents a major cause of discoloration or
bility of regulatory limitations prior to use.
disfigurement of painted surfaces. This practice covers the
2. Referenced Documents preparation of coatings for testing, their application on sub-
strates, and the arrangement of the coated panels on exterior
2.1 ASTM Standards:
test fences to determine the degree of microbiological attack
D 1006 Practice for Conducting Exterior Exposure Tests of
that may occur on the surface of the coatings over a period of
Paints on Wood
time. This practice is intended to provide guidelines for, and a
D 1849 Test Method for Package Stability of Paint
discussion of, the various factors critical in selection of exterior
D 3274 Test Method of Evaluating Degree of Surface Dis-
coatings resistant to discoloration or disfigurement by algae
figurement of Paint Films by Microbial (Fungal or Algal)
and fungi.
Growth or Soil and Dirt Accumulation
5. Preparation and Application of Coatings
3. Summary of Practice
5.1 Conditioning of Coatings Prior to Application—
3.1 Simple observation of a coated object subjected to
Individual coatings to be used in the paint system should be
exterior exposure is considered a practical and reliable method
properly aged under suitable conditions prior to testing. Hy-
for determining the degree that microorganisms discolor the
drolysis, amalgamation, absorption, and other physical and
coating. However, this applies to a specific coated object
chemical changes that may have a profound influence on the
exposed under a given set of conditions. It should be recog-
resistance of a coating to microorganisms usually increase with
nized that there are critical factors that influence the amount of
increasing temperature. It is recognized that actual storage
fungal growth that may occur on the same coated object when
periods of paints prior to use may vary from one to several
exposed to other conditions. These factors include the geo-
years, and the peak temperature encountered may be as warm
graphic location, local atmospheric conditions such as the dust
as 160°F (70°C). However, a recommended conditioning
and pollen content of the air, angle of exposure, degree to
period consists of 1 year at room temperatures or 1 month at
which the coating is subjected to weathering, effects of
125°F (50°C) as in Test Method D 1849. The conditioning of
moisture and sunlight, the substrates on which the coating is
coatings prior to testing shall be agreeable to the producer and
applied, and the coatings in the paint system under test. The
the user in the case of a referee test.
5.2 Preparation of Coatings for Application—Prior to ap-
This practice is under the jurisdiction of ASTM Committee D-1 on Paint, and
plication of the various coatings to be included in the total paint
Related Coatings, Materials, and Applications and is the direct responsibility of
system, thoroughly reconstitute each coating by appropriate
Subcommittee D01.28 on Biodeterioration.
Current edition approved March 27, 1986. Published May 1986. Originally
mixing or shaking. At the time of application, there must be no
e1
published as D 3456 – 75. Last previous edition D 3456 – 75 (1981)
settling, incompatibility, or other stability problem observable
Annual Book of ASTM Standards, Vol 06.01.
3 in the coating in the container.
Annual Book of ASTM Standards, Vol 06.02.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3456
5.3 Application of Paint System—Apply each coating in the stability, resulting in microcracking of coatings applied on the
total paint system in an appropriate manner to provide a wood with subsequent mold growth in these cracks. Plywood,
specified and reasonably uniform film thickness. The presence hardboard, and other wood-derived products support varying
and thickness of different coatings in the complete system can degrees of fungal growth depending on the nutrient value,
have a pronounced effect on the degree of microbiological degree of moisture absorption, and dimensional stability of the
discoloration that will occur. Thus, each paint in the system base material. Redwood tends to have better dimensional
must be applied as recommended by the manufacturer. It is stability and otherwise has insignificant effect on the micro-
important that the procedure and the user agree on the type of biological growth on coatings applied over it. Cedar lumber
coatings and the spreading rate of each coating in the final test generally contains compounds that aid in resisting microbio-
film. The drying time between coats and the curing time of the logical growth. Both cedar and redwood contain colored
total system prior to exposure should also be specified. extractives that can bleed through coatings to discolor the
Recommended practice for house paint is 2 days between coats surface. Some of these extractives can also be nutrients that
and no less than 7 days and not longer than 1 month prior to the contribute to microbiological growth, resulting in added dis-
exterior exposure. Industrial and industrial maintenance coat- coloration.
ings may require a different practice that should be acceptable 6.3 Metal Substrates—Iron, galvanized steel, and aluminum
to the producer and the user. are common substrates for paints. Iron and zinc compounds
5.4 . On each substrate use a test area not less than 48 in. generally inhibit microbiological growth. On the other hand,
(310 cm ) in size. When only one type of substrate is being these metals may react with certain microbiocides to reduce the
used, expose at least duplicate panels. When more than one microbiological inhibition. Certain microbiocides can also
substrate is employed for each exposure condition, duplicate cause discolored corrosion products or loss of adhesion by the
panels of each substrate are not usually required. In case of a coating on these surfaces. Aluminum is rather chemically inert
referee test, it is recommended that replication and size of test and does not itself promote microbiological growth. It may,
area be agreed on between the producer and the user. Common however, cause loss of microbiological resistance of coatings
practice in the industry is to use 6 in. (nominal) by 36-in. (152 containing certain mercury compounds because of the amal-
by 915-mm) panels for house paint exposures and to use 12-in. gamation reaction by aluminum and mercury. This can result in
(305-mm) metal panels of various widths for exposures of loss of adhesion.
industrial and industrial maintenance coatings. 6.4 Masonry Substrates—The extremes of masonry sur-
faces generally consist of two conditions: fresh surfaces, which
6. Substrates for Testing
are relatively alkaline and free of fungi and algae, and
6.1 General Considerations—The substrate on which a
weathered surfaces that are less alkaline and may be discolored
paint system is exposed can have a significant effect on the
because of microbiologica
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