ASTM B940-05(2020)
(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
SIGNIFICANCE AND USE
4.1 This practice is applicable to non-chromate coatings that are colorless, colored, electrochemically applied or non-electrochemically applied. The zinc or cadmium, or both, may be electrodeposited, mechanically deposited, hot-dipped, rolled, or in the form of castings.
4.2 Because of variables inherent in the salt-spray test which may differ from one test cabinet to another, interpretation of test results for compliance with expected performance should be specified by the purchaser.
4.3 Properties such as thickness, color, luster, and ability to provide good paint adhesion are not covered in this practice, nor are the chemical composition and the method of application of these finishes.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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.
General Information
Relations
Standards Content (Sample)
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: B940 − 05 (Reapproved 2020)
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.
1. Scope 3. Terminology
3.1 Descriptions of Terms:
1.1 This practice covers a procedure for evaluating the
3.1.1 time to failure—time to failure will depend on the type
protective value of chemical and electrochemical conversion
of coating tested. The minimum expected protective value
coatingsproducedbynon-chromate(chromatebeingdefinedas
obtainable in a given salt spray test is given in Appendix X2.
a compound that has chromium in the plus six oxidation state,
3.1.1.1 Discussion—In most instances, failure is defined as
and as such, chromium compounds in other oxidation states,
the first appearance on significant surfaces of white corrosion
suchasplusthree,shallnotbeexcluded)treatmentsofzincand
products visible to the unaided eye at normal reading distance,
cadmium surfaces.
except that the presence of white corrosion products at sharp
1.2 The protective value of a non-chromate coating is
edges (for example, on threaded fasteners) and at junctions
usually determined by salt-spray test and by determining
between dissimilar metals should not be considered failure. In
whether or not the coating possesses adequate abrasion resis-
some instances, it may be desirable to regard the first appear-
tance when applied for that purpose.
ance of red rust as failure.
1.3 The values stated in SI units are to be regarded as
3.1.2 significant surfaces—in general, significant surfaces
standard. No other units of measurement are included in this
are those surfaces that are visible and subject to corrosion or
standard.
wear, or both, except that surfaces that are normally difficult to
coat by electroplating or mechanical deposition may be ex-
1.4 This standard does not purport to address all of the
empt. The designation of significant surfaces may be indicated
safety concerns, if any, associated with its use. It is the
on the drawing.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Significance and Use
mine the applicability of regulatory limitations prior to use.
4.1 This practice is applicable to non-chromate coatings that
1.5 This international standard was developed in accor-
are colorless, colored, electrochemically applied or non-
dance with internationally recognized principles on standard-
electrochemically applied. The zinc or cadmium, or both, may
ization established in the Decision on Principles for the
be electrodeposited, mechanically deposited, hot-dipped,
Development of International Standards, Guides and Recom-
rolled, or in the form of castings.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4.2 Because of variables inherent in the salt-spray test
which may differ from one test cabinet to another, interpreta-
2. Referenced Documents
tion of test results for compliance with expected performance
should be specified by the purchaser.
2.1 ASTM Standards:
B117 Practice for Operating Salt Spray (Fog) Apparatus 4.3 Properties such as thickness, color, luster, and ability to
provide good paint adhesion are not covered in this practice,
nor are the chemical composition and the method of applica-
tion of these finishes.
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
5. Conditioning
Conversion Coatings.
Current edition approved May 1, 2020. Published May 2020. Originally
5.1 Aging—Before subjecting a non-chromate coating to
approvedin2000.Lastpreviouseditionapprovedin2014asB940 –05(2014).DOI:
test, check with the chemical producer to determine if aging is
10.1520/B0940-05R20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or an issue that needs to be considered.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.2 Preparation of Specimen—The test surface must be free
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. of fingerprints and other extraneous stains and must not be
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