ASTM B696-00(2009)
(Specification)Standard Specification for Coatings of Cadmium Mechanically Deposited
Standard Specification for Coatings of Cadmium Mechanically Deposited
ABSTRACT
This specification covers the requirements for coating of cadmium mechanically deposited on metal products. Cadmium coatings shall classified on the basis of thickness, as follows: Class 12; Class 8; and Class 5. Cadmium coatings shall be identified as Type I and Type II on the basis of supplementary treatment required. The coating shall be uniform in appearance and free of blisters, pits, nodules, flaking, and other defects that can adversely affect the function of the coating. All steel parts that have ultimate tensile strength and that contains tensile stresses caused by machining, grinding, straightening, or cold-forming operation shall be given a stress relief heat treatment prior to cleaning and metal deposition. The minimum hours to failure (appearance of white corrosion products and red rust for mechanically deposited cadmium coatings on iron and steel) of Type I and Type II coatings shall be indicated to guarantee satisfactory performance. The test specimen shall undergo adhesion, corrosion resistance, and appearance tests. The thickness of the coating shall be determined by the microscopical method, or the magnetic method, or the beta backscatter method, as applicable.
SCOPE
1.1 This specification covers the requirements for a coating of cadmium mechanically deposited on metal products. The coating is provided in various thicknesses up to and including 12 μm.
1.2 Mechanical deposition greatly reduces the risk of hydrogen embrittlement and is suitable for coating bores and recesses in many parts that cannot be conveniently electroplated (see Appendix X3).
1.3 Cadmium coatings are usually applied to provide engineering properties and corrosion resistance. The performance of a cadmium coating depends largely on its thickness and the kind of environment to which it is exposed. Without proof of satisfactory correlation, accelerated tests such as the salt spray (fog) test cannot be relied upon to predict performance in other environments, nor will these serve as comparative measures of the corrosion resistance afforded by coatings of different metals. Thus, although there is a marked superiority of cadmium coatings over zinc coatings of equal thickness in the salt spray test, this is often not the case under conditions of use, so that further testing in the service environment should be conducted.
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 and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see 1.5 and 1.6.
1.5 Warning—Cadmium is toxic and must not be used in a coating for articles that can come into contact with food or beverages, or for dental or other equipment that can be inserted into the mouth. Consult appropriate agencies for regulations in this connection.
1.6 Warning—Because of the toxicity of cadmium vapors and cadmium oxide fumes, cadmium-coated articles must not be used at temperatures of 320°C and above. They must not be welded, spot-welded, soldered, or otherwise strongly heated without adequate ventilation that will efficiently remove all toxic fumes.
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Designation:B696 −00(Reapproved2009)
Standard Specification for
Coatings of Cadmium Mechanically Deposited
This standard is issued under the fixed designation B696; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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 beusedattemperaturesof320°Candabove.Theymustnotbe
welded, spot-welded, soldered, or otherwise strongly heated
1.1 This specification covers the requirements for a coating
without adequate ventilation that will efficiently remove all
of cadmium mechanically deposited on metal products. The
toxic fumes.
coating is provided in various thicknesses up to and including
12 µm.
2. Referenced Documents
1.2 Mechanical deposition greatly reduces the risk of hy-
2.1 ASTM Standards:
drogen embrittlement and is suitable for coating bores and
B117Practice for Operating Salt Spray (Fog) Apparatus
recesses in many parts that cannot be conveniently electro-
B183Practice for Preparation of Low-Carbon Steel for
plated (see Appendix X3).
Electroplating
1.3 Cadmium coatings are usually applied to provide engi-
B242Guide for Preparation of High-Carbon Steel for Elec-
neering properties and corrosion resistance. The performance
troplating
of a cadmium coating depends largely on its thickness and the
B322Guide for Cleaning Metals Prior to Electroplating
kind of environment to which it is exposed. Without proof of
B487Test Method for Measurement of Metal and Oxide
satisfactory correlation, accelerated tests such as the salt spray
Coating Thickness by Microscopical Examination of
(fog)testcannotbereliedupontopredictperformanceinother
Cross Section
environments, nor will these serve as comparative measures of
B499Test Method for Measurement of CoatingThicknesses
the corrosion resistance afforded by coatings of different
by the Magnetic Method: Nonmagnetic Coatings on
metals. Thus, although there is a marked superiority of cad-
Magnetic Basis Metals
mium coatings over zinc coatings of equal thickness in the salt
B567Test Method for Measurement of Coating Thickness
spray test, this is often not the case under conditions of use, so
by the Beta Backscatter Method
that further testing in the service environment should be
B602Test Method for Attribute Sampling of Metallic and
conducted.
Inorganic Coatings
1.4 This standard does not purport to address all of the B697Guide for Selection of Sampling Plans for Inspection
of Electrodeposited Metallic and Inorganic Coatings
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- B762Test Method of Variables Sampling of Metallic and
Inorganic Coatings
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific F1470Practice for Fastener Sampling for Specified Me-
chanical Properties and Performance Inspection
precautionary statements, see 1.5 and 1.6.
1.5 Warning—Cadmium is toxic and must not be used in a
3. Classification
coating for articles that can come into contact with food or
beverages,orfordentalorotherequipmentthatcanbeinserted
3.1 Classes—Cadmium coatings are classified on the basis
into the mouth. Consult appropriate agencies for regulations in
of thickness, as follows:
this connection.
Class Minimum Thickness, µm
12 12
1.6 Warning—Because of the toxicity of cadmium vapors
and cadmium oxide fumes, cadmium-coated articles must not
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee
B08.06 on Soft Metals. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Sept. 1, 2009. Published December 2009. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
approved in 1981. Last previous edition approved in 2004 as B696–00(2004) . Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/B0696-00R09. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B696−00(2009)
3.2 Types—Cadmiumcoatingsareidentifiedbytypesonthe 6.2.2 High-strength steels that have heavy oxide or scale
basis of supplementary treatment required, as follows: shallbecleanedbeforeapplicationofthecoatinginaccordance
Type I—As coated without supplementary chromate treat- with Practice B242. In general, nonelectrolytic alkaline,
ment (Appendix X2.1). anodic-alkaline, and some inhibited acid cleaners are preferred
Type II—With colored chromate conversion treatment (Ap- toavoidtheriskofproducinghydrogenembrittlementfromthe
pendix X2.2). cleaning procedure.
6.2.3 For low-carbon steels see Practice B183. Useful
4. Ordering Information
guidelines are also given in Practice B322.
6.2.4 Supplementary Treatments:
4.1 To make the application of this standard complete, the
purchasershouldsupplythefollowinginformationtotheseller 6.2.4.1 Colored Chromate Conversion Treatments (Type
in the purchase order or other governing document: II)—ChromatetreatmentforTypeIIshallbedoneinasolution
4.1.1 Class, including a maximum thickness, if appropriate, containinghexavalentchromium.Thissolutionshallproducea
Type, and for Type II, color and need for supplemental bright or semi-bright continuous, smooth, protective film with
lubricant (see 3.1, 3.2, and 6.2.4.2), a uniform color that may range from yellow through bronze
andolivedrabtobrownandblackincludingolivedrabandthat
4.1.2 Nature of substrate (for example, high-strength steel),
needed for stress relief (6.2.1), and cleaning precautions to be may be dyed to a desired color. Post treatments that do not
contain salts that yield films containing hexavalent chromium
followed 6.2.2 and 6.2.3),
4.1.3 Significant surfaces (6.3), are not permitted as treatments for producingType II coatings.
4.1.4 Requirements for and methods of testing for one or 6.2.4.2 Waxes, lacquers, or other organic coatings may be
more of the following, if required: need for and type of test used to improve lubricity, and the need for them shall be
specimens (8.1), thickness (6.3 and 8.3), adhesion (6.4 and supplied in the purchase order or other governing document
8.4), corrosion resistance (6.5 and 8.5), absence of hydrogen (4.1.1).Supplementallubricationtreatmentshallnotbeusedto
embrittlement,andthewaitingperiodbeforetestingandtesting ensure conformance to the salt spray corrosion resistance
loads (6.6 and 8.6), requirements.
4.1.5 Inspection responsibility (Supplementary Require- 6.2.5 Surface Defects—Defects and variations in appear-
ment S1) and sampling plan for each inspection criterion
ance in the coating that arise from surface conditions of the
(Section 7). substrate(scratches,pores,rollmarks,inclusions,andsoforth)
4.1.6 Requirements for certified report of test results (Sec-
and that persist in the finish despite the observance of good
tion 10). metal finishing practices shall not be cause for rejection.
NOTE 2—Applied finishes generally perform better in service when the
5. Workmanship
substrate over which they are applied is smooth and free of torn metal,
5.1 The coating shall be uniform in appearance and free of inclusions, pores, and other defects. It is recommended that the specifi-
cationscoveringtheunfinishedproductprovidelimitsforthesedefects.A
blisters, pits, nodules, flaking, and other defects that can
metal finisher can often remove defects through special treatments, such
adversely affect the function of the coating. The coating shall
as grinding, polishing, abrasive blasting, chemical treatments, and elec-
cover all surfaces as stated in 6.3 including roots of threads,
tropolishing. However, these are not normal in the treatment steps
thread peaks, corners, recesses, and edges. The coating shall
preceding the application of the finish. When desired they must be
notbestainedordiscoloredthroughouttoanextentthatwould specified on the purchase order (4.1.2).
adversely affect appearance as a functional requirement.
6.3 Thickness:
However, superficial staining that results from rinsing or
6.3.1 The thickness of the coating everywhere on the
drying and variations in color or luster shall not be cause for
significant surfaces shall be at least that of the specified class
rejection.
as defined in 3.1.
6.3.2 Significant surfaces are defined as those normally
NOTE 1—The nature of the mechanical plating process is such that
coatings characteristically will not be as smooth or as bright as some
visible (directly or by reflection) that are essential to the
electroplated coatings.
appearance or serviceability of the article when assembled in
normalposition;orthatcanbethesourceofcorrosionproducts
6. Requirements
that deface visible surfaces on the assembled article. When
6.1 Appearance—The coating as deposited shall have a
necessary, the significant surfaces shall be indicated on the
uniform silvery appearance, and a matte to medium-bright
drawing for the article, or by the provision of suitably marked
luster.
samples.
6.2 Process:
NOTE3—Thethicknessofmechanically-depositedcoatingsvariesfrom
6.2.1 Stress-Relief Treatment—All steel parts that have ul-
point-to-point on the surface of a product, characteristically tending to be
timatetensilestrengthof1000MPaandaboveandthatcontain
thicker on flat surfaces and thinner at exposed edges, sharp projections,
shielded or recessed areas, interior corners and holes, with such thinner
tensile stresses caused by machining, grinding, straightening,
areas often being exempted from thickness requirements.
or cold-forming operation shall be given a stress relief heat
treatment prior to cleaning and metal deposition.The tempera- 6.3.3 When significant surfaces are involved on which the
ture and time at temperature shall be 190 6 15°C for a specified thickness of deposit cannot readily be controlled, the
minimum of3hso that maximum stress relief is obtained purchaser and manufacturer should recognize the necessity for
without reducing the hardness below the specified minimum. either thicker or thinner deposits. For example, to reduce
B696−00(2009)
tested materials in all environments where these materials may be used.
buildup in thread roots, holes, deep recesses, bases of angles,
Also,performanceofdifferentmaterialsinthetestcannotalwaysbetaken
and similar areas, the deposit thickness on the more accessible
as a direct guide to the relative corrosion resistance of these materials in
surfaces will have to be reduced proportionately.
service.
NOTE 4—The coating thickness requirement of this specification is a
6.5.3 On parts with Type II coatings, the greater number of
minimumrequirement;thatis,thecoatingthicknessisrequiredtoequalor
hours for either white corrosion products or rust shall apply.
exceed the specified thickness everywhere on the significant surfaces.
For example, for Type II, Class 5, the test shall be continued
Variation in the coating thickness from point to point on a coated article
until the 72-h requirement is met for white corrosion products;
is an inherent characteristic of mechanical deposition processes.
Therefore, the coating thickness will have to exceed the specified value at
similarly, for Type II, Class 8, if no white corrosion products
some points on the significant surfaces to ensure that the thickness equals
appear before 72 h, the test shall be continued until the 96-h
or exceeds the specified value at all points. Hence, in most cases, the
requirement for basis metal corrosion is met (8.5.2).
average coating thickness on an article will be greater than the specified
value; how much greater is largely determined by the shape of the article
6.6 Absence of Hydrogen Embrittlement—Steel springs and
and the characteristics of the deposition process. In addition, the average
other high-strength steel parts subject to flexure shall be held
coating thickness on articles will vary from article to article within a
foraminimumof48hatroomtemperatureaftercoatingbefore
production lot. Therefore, if all of the articles in a production lot are to
being loaded, flexed, or used. Such high-strength steel parts
meet the thickness requirement, the average coating thickness for the
production lot as a whole will be greater than the average necessary to
shall be free of hydrogen embrittlement.When specified in the
ensure that a single article meets the requirement.
purchase order, freedom from embrittlement shall be deter-
6.4 Adhesion—The cadmium coating shall be sufficiently
mined by the test specified herein (4.1.4 and 8.6).
adherent to the basis metal to pass the tests specified in 8.4.
7. Sampling
6.5 Corrosion Resistance:
6.5.1 The presence of corrosion products visible to the
7.1 The purchaser and producer are urged to employ statis-
unaided eye at normal reading distance at the end of the
tical process control in the coating process. Properly
specified test periods stated in Table 1 shall constitute failure,
performed, statistical process control will assure coated prod-
except that corrosion products at edges of specimens shall not
ucts of satisfactory quality and will reduce the amount of
constitute failure. Slight “wisps” of white corrosion, as op-
acceptance inspection. The sampling plan used for the inspec-
posed to obvious accumulations, shall be acceptable.
tion of the quality coated article shall be agreed upon between
the purchaser and producer.
NOTE 5—The hours given in Table 1 are the minimums required to
7.1.1 When a collection of coated articles (inspection lot,
guaranteesatisfactoryperformance.Longerperiodsbeforetheappearance
of white corrosion products and rust are possible, but salt spray resistance
see 7.2) is examined for compliance with the requirements
does not vary in exact proportion with increased plating thickness. The
placed on the articles, a relatively small number of the articles
hoursgivenforTypeIIreflecttheaddedprotectionofchromatetreatments
(sample)isselectedatrandomandisinspected.Theinspection
without requiring impractical testing periods.
lot is then classified as complying with the requirements based
6.5.2 There are no requirements for corrosion of basis
on the results of the inspection of the sample. The size of the
metals other than steels.
sample and the criteria for compliance are determined by the
application of statistics. The procedure is known as sampling
NOTE 6—Mechanical deposition is exclusively a barrel-finishing pro-
cess. It is recognized
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