ASTM B940-05
(Practice)Standard Practice for Testing Non-Chromate Coatings on Zinc and Cadmium Surfaces
Standard Practice for Testing Non-Chromate Coatings on Zinc and Cadmium Surfaces
SCOPE
1.1 This practice covers a procedure for evaluating the protective value of chemical and electrochemical conversion coatings produced by non-chromate (chromate being defined as a compound that has chromium in the plus six oxidation state, and as such, chromium compounds in other oxidation states, such as plus three, shall not be excluded) treatments of zinc and cadmium surfaces.
1.2 The protective value of a non-chromate coating is usually determined by salt-spray test and by determining whether or not the coating possesses adequate abrasion resistance when applied for that purpose.
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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Designation:B940–05
Standard Practice for
Testing Non-Chromate Coatings on Zinc and Cadmium
Surfaces
This standard is issued under the fixed designation B940; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope some instances, it may be desirable to regard the first appear-
ance of red rust as failure.
1.1 This practice covers a procedure for evaluating the
3.1.2 significant surfaces—in general, significant surfaces
protective value of chemical and electrochemical conversion
are those surfaces that are visible and subject to corrosion or
coatingsproducedbynon-chromate(chromatebeingdefinedas
wear, or both, except that surfaces that are normally difficult to
a compound that has chromium in the plus six oxidation state,
coat by electroplating or mechanical deposition may be ex-
and as such, chromium compounds in other oxidation states,
empt. The designation of significant surfaces may be indicated
suchasplusthree,shallnotbeexcluded)treatmentsofzincand
on the drawing.
cadmium surfaces.
1.2 The protective value of a non-chromate coating is
4. Significance and Use
usually determined by salt-spray test and by determining
4.1 This practice is applicable to non-chromate coatings that
whether or not the coating possesses adequate abrasion resis-
are colorless, colored, electrochemically applied or non-
tance when applied for that purpose.
electrochemically applied. The zinc or cadmium, or both, may
1.3 This standard does not purport to address all of the
be electrodeposited, mechanically deposited, hot-dipped,
safety concerns, if any, associated with its use. It is the
rolled, or in the form of castings.
responsibility of the user of this standard to establish appro-
4.2 Because of variables inherent in the salt-spray test
priate safety and health practices and determine the applica-
which may differ from one test cabinet to another, interpreta-
bility of regulatory limitations prior to use.
tion of test results for compliance with expected performance
2. Referenced Documents should be specified by the purchaser.
4.3 Properties such as thickness, color, luster, and ability to
2.1 ASTM Standards:
provide good paint adhesion are not covered in this practice,
B117 Practice for Operating Salt Spray (Fog) Apparatus
nor are the chemical composition and the method of applica-
3. Terminology tion of these finishes.
3.1 Descriptions of Terms:
5. Conditioning
3.1.1 time to failure—time to failure will depend on the type
5.1 Aging—Before subjecting a non-chromate coating to
of coating tested. The minimum expected protective value
test, check with the chemical producer to determine if aging is
obtainable in a given salt spray test is given in Appendix X2.
an issue that needs to be considered.
3.1.1.1 Discussion—In most instances, failure is defined as
5.2 Preparation of Specimen—The test surface must be free
the first appearance on significant surfaces of white corrosion
of fingerprints and other extraneous stains and must not be
products visible to the unaided eye at normal reading distance,
cleaned except by gentle wiping with a clean, dry, soft cloth to
except that the presence of white corrosion products at sharp
remove loose particles. Oily or greasy surfaces should not be
edges (for example, on threaded fasteners) and at junctions
used for testing, and degreasing with organic solvents is not
between dissimilar metals should not be considered failure. In
recommended.
6. Procedure
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 on
6.1 Salt Spray Test—Expose the clean specimen to a 5 %
Chromate Conversion Coatings.
solution salt spray and conduct the test in accordance with the
Current edition approved Oct. 1, 2005. Published October 2005. DOI: 10.1520/
B0940-05.
latest revision of Practice B117. Unless otherwise specified,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
only those surfaces that are positioned in the test chamber in
contact ASTM Customer Service at servi
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