ASTM B696-00(2004)e1
(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 m.
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 ).
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.
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.
1.4 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.
1.5 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 (Reapproved 2004)
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. 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.
´ NOTE—The Warning notes in 1.5 and 1.6 were editorially updated in October 2004.
1. Scope be used at temperatures of 320°C and above. They must not be
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
B117 Practice for Operating Salt Spray (Fog) Apparatus
recesses in many parts that cannot be conveniently electro-
B183 Practice for Preparation of Low-Carbon Steel for
plated (see Appendix X3).
Electroplating
1.3 Cadmium coatings are usually applied to provide engi-
B242 Guide 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
B322 Guide for Cleaning Metals Prior to Electroplating
kind of environment to which it is exposed. Without proof of
B487 Test Method for Measurement of Metal and Oxide
satisfactory correlation, accelerated tests such as the salt spray
CoatingThicknessbyMicroscopicalExaminationofCross
(fog) test cannot be relied upon to predict performance in other
Section
environments, nor will these serve as comparative measures of
B499 Test Method for Measurement of Coating Thick-
the corrosion resistance afforded by coatings of different
nessesbytheMagneticMethod:NonmagneticCoatingson
metals. Thus, although there is a marked superiority of cad-
Magnetic Basis Metals
mium coatings over zinc coatings of equal thickness in the salt
B567 Test 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
B602 Test Method for Attribute Sampling of Metallic and
conducted.
Inorganic Coatings
1.4 This standard does not purport to address all of the
B697 Guide for Selection of Sampling Plans for Inspection
safety concerns, if any, associated with its use. It is the
of Electrodeposited Metallic and Inorganic Coatings
responsibility of the user of this standard to establish appro-
B762 Test Method of Variables Sampling of Metallic and
priate safety and health practices and determine the applica-
Inorganic Coatings
bility of regulatory limitations prior to use. For specific
F1470 Practice for Fastener Sampling for Specified Me-
precautionary statements, see 1.5 and 1.6.
chanical Properties and Performance Inspection
1.5 Warning—Cadmium is toxic and must not be used in a
coating for articles that can come into contact with food or
3. Classification
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
1.6 Warning—Because of the toxicity of cadmium vapors
12 12
and cadmium oxide fumes, cadmium-coated articles must not
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.08.04 on Soft Metals. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2004. Published October 2004. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1981. Last previous edition approved in 2000 as B696 – 00. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0696-00R04E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B696 – 00 (2004)
3.2 Types—Cadmiumcoatingsareidentifiedbytypesonthe with Practice B242. In general, nonelectrolytic alkaline,
basis of supplementary treatment required, as follows: anodic-alkaline, and some inhibited acid cleaners are preferred
Type I—As coated without supplementary chromate treat- toavoidtheriskofproducinghydrogenembrittlementfromthe
ment (Appendix X2.1). cleaning procedure.
Type II—With colored chromate conversion treatment (Ap-
6.2.3 For low-carbon steels see Practice B183. Useful
pendix X2.2). guidelines are also given in Practice B322.
6.2.4 Supplementary Treatments:
4. Ordering Information
6.2.4.1 Colored Chromate Conversion Treatments (Type
4.1 To make the application of this standard complete, the
II)—Chromate treatment forType II shall be done in a solution
purchaser should supply the following information to the seller
containing hexavalent chromium.This solution shall produce a
in the purchase order or other governing document:
bright or semi-bright continuous, smooth, protective film with
4.1.1 Class, including a maximum thickness, if appropriate,
a uniform color that may range from yellow through bronze
Type, and for Type II, color and need for supplemental
andolivedrabtobrownandblackincludingolivedrabandthat
lubricant (see 3.1, 3.2, and 6.2.4.2),
may be dyed to a desired color. Post treatments that do not
4.1.2 Nature of substrate (for example, high-strength steel),
contain salts that yield films containing hexavalent chromium
needed for stress relief (6.2.1), and cleaning precautions to be
are not permitted as treatments for producing Type II coatings.
followed 6.2.2 and 6.2.3),
6.2.4.2 Waxes, lacquers, or other organic coatings may be
4.1.3 Significant surfaces (6.3),
used to improve lubricity, and the need for them shall be
4.1.4 Requirements for and methods of testing for one or
supplied in the purchase order or other governing document
more of the following, if required: need for and type of test
(4.1.1). Supplemental lubrication treatment shall not be used to
specimens (8.1), thickness (6.3 and 8.3), adhesion (6.4 and
ensure conformance to the salt spray corrosion resistance
8.4), corrosion resistance (6.5 and 8.5), absence of hydrogen
requirements.
embrittlement,andthewaitingperiodbeforetestingandtesting
6.2.5 Surface Defects—Defects and variations in appear-
loads (6.6 and 8.6),
ance in the coating that arise from surface conditions of the
4.1.5 Inspection responsibility (Supplementary Require-
substrate (scratches, pores, roll marks, inclusions, and so forth)
ment S1) and sampling plan for each inspection criterion
and that persist in the finish despite the observance of good
(Section 7).
metal finishing practices shall not be cause for rejection.
4.1.6 Requirements for certified report of test results (Sec-
tion 10). NOTE 2—Applied finishes generally perform better in service when the
substrate over which they are applied is smooth and free of torn metal,
5. Workmanship inclusions, pores, and other defects. It is recommended that the specifi-
cations covering the unfinished product provide limits for these defects.A
5.1 The coating shall be uniform in appearance and free of
metal finisher can often remove defects through special treatments, such
blisters, pits, nodules, flaking, and other defects that can
as grinding, polishing, abrasive blasting, chemical treatments, and elec-
adversely affect the function of the coating. The coating shall
tropolishing. However, these are not normal in the treatment steps
cover all surfaces as stated in 6.3 including roots of threads,
preceding the application of the finish. When desired they must be
thread peaks, corners, recesses, and edges. The coating shall specified on the purchase order (4.1.2).
not be stained or discolored throughout to an extent that would
6.3 Thickness:
adversely affect appearance as a functional requirement. How-
6.3.1 The thickness of the coating everywhere on the
ever, superficial staining that results from rinsing or drying and
significant surfaces shall be at least that of the specified class
variations in color or luster shall not be cause for rejection.
as defined in 3.1.
NOTE 1—The nature of the mechanical plating process is such that
6.3.2 Significant surfaces are defined as those normally
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:
6.2.1 Stress-Relief Treatment—All steel parts that have NOTE 3—Thethicknessofmechanically-depositedcoatingsvariesfrom
point-to-point on the surface of a product, characteristically tending to be
ultimate tensile strength of 1000 MPa and above and that
thicker on flat surfaces and thinner at exposed edges, sharp projections,
contain tensile stresses caused by machining, grinding,
shielded or recessed areas, interior corners and holes, with such thinner
straightening, or cold-forming operation shall be given a stress
areas often being exempted from thickness requirements.
relief heat treatment prior to cleaning and metal deposition.
The temperature and time at temperature shall be 190 6 15°C 6.3.3 When significant surfaces are involved on which the
for a minimum of3hso that maximum stress relief is obtained specified thickness of deposit cannot readily be controlled, the
without reducing the hardness below the specified minimum. purchaser and manufacturer should recognize the necessity for
6.2.2 High-strength steels that have heavy oxide or scale either thicker or thinner deposits. For example, to reduce
shallbecleanedbeforeapplicationofthecoatinginaccordance buildup in thread roots, holes, deep recesses, bases of angles,
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B696 – 00 (2004)
tested materials in all environments where these materials may be used.
and similar areas, the deposit thickness on the more accessible
Also,performanceofdifferentmaterialsinthetestcannotalwaysbetaken
surfaces will have to be reduced proportionately.
as a direct guide to the relative corrosion resistance of these materials in
NOTE 4—The coating thickness requirement of this specification is a
service.
minimumrequirement;thatis,thecoatingthicknessisrequiredtoequalor
6.5.3 On parts with Type II coatings, the greater number of
exceed the specified thickness everywhere on the significant surfaces.
Variation in the coating thickness from point to point on a coated article hours for either white corrosion products or rust shall apply.
is an inherent characteristic of mechanical deposition processes. There-
For example, for Type II, Class 5, the test shall be continued
fore, the coating thickness will have to exceed the specified value at some
until the 72-h requirement is met for white corrosion products;
points on the significant surfaces to ensure that the thickness equals or
similarly, for Type II, Class 8, if no white corrosion products
exceeds the specified value at all points. Hence, in most cases, the average
appear before 72 h, the test shall be continued until the 96-h
coating thickness on an article will be greater than the specified value;
requirement for basis metal corrosion is met (8.5.2).
how much greater is largely determined by the shape of the article and the
6.6 Absence of Hydrogen Embrittlement—Steel springs and
characteristics of the deposition process. In addition, the average coating
thickness on articles will vary from article to article within a production
other high-strength steel parts subject to flexure shall be held
lot. Therefore, if all of the articles in a production lot are to meet the
foraminimumof48hatroomtemperatureaftercoatingbefore
thicknessrequirement,theaveragecoatingthicknessfortheproductionlot
being loaded, flexed, or used. Such high-strength steel parts
as a whole will be greater than the average necessary to ensure that a
shall be free of hydrogen embrittlement. When specified in the
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.
6.5 Corrosion Resistance:
7. Sampling
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 per-
specified test periods stated in Table 1 shall constitute failure,
formed, statistical process control will assure coated products
except that corrosion products at edges of specimens shall not
of satisfactory quality and will reduce the amount of accep-
constitute failure. Slight “wisps” of white corrosion, as op-
tance inspection. The sampling plan used for the inspection of
posed to obvious accumulations, shall be acceptable.
the quality coated article shall be agreed upon between the
NOTE 5—The hours given in Table 1 are the minimums required to
purchaser and producer.
guarantee satisfactory performance. Longer periods before the appearance
7.1.1 When a collection of coated articles (inspection lot,
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
without requiring impractical testing periods. (sample) is selected at random and is inspected.The inspection
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 a
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