ASTM B635-00(2009)
(Specification)Standard Specification for Coatings of Cadmium-Tin Mechanically Deposited
Standard Specification for Coatings of Cadmium-Tin Mechanically Deposited
ABSTRACT
This specification covers the requirements for a coating that is a mixture of cadmium and tin mechanically deposited on metal products. The coating shall be 45 to 75 mass % cadmium, the remainder tin. All steel parts that have ultimate tensile strength of 1000 MPa and above and that contain 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. High-strength steels that have heavy oxide or scale shall be cleaned before application of the coating in accordance with guide B 242. Chromate treatment for Type II shall be done in a solution containing hexavalent chromium. The cadmium-tin coating shall be sufficiently adherent to the basis metal to pass the prescribed testing. Steel springs and other high-strength steel parts shall be free from hydrogen embrittlement. The coating shall be uniform in appearance and substantially free of blisters, pits, nodules, flaking and other defects that can adversely affect the function of the coating. Chemical composition of the cadmium-tin coating shall be determined when required on the purchase order by procedures given in methods E 87 or test methods E 396. The thickness of the coating shall be determined by the microscopical method, the magnetic method, or the beta backscatter method as applicable. Chromate conversion coatings of cadmium-tin both have an essentially silvery-white appearance. Adhesion of the cadmium-tin deposit to the basis metal shall be tested in a manner that is consistent with the service requirements of the coated article. Coated parts to be tested for the absence of embrittlement from cleaning shall be tested for brittle failure in accordance with a suitable method.
SCOPE
1.1 This specification covers the requirements for a coating that is a mixture of cadmium and tin 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 plated electrolytically. (See Appendix X1.)
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 and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements, see Section 7.
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Designation:B635 −00(Reapproved2009)
Standard Specification for
Coatings of Cadmium-Tin Mechanically Deposited
This standard is issued under the fixed designation B635; 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.
1. Scope by the Magnetic Method: Nonmagnetic Coatings on
Magnetic Basis Metals
1.1 This specification covers the requirements for a coating
B567Test Method for Measurement of Coating Thickness
thatisamixtureofcadmiumandtinmechanicallydepositedon
by the Beta Backscatter Method
metal products. The coating is provided in various thicknesses
B571Practice for Qualitative Adhesion Testing of Metallic
up to and including 12 µm.
Coatings
1.2 Mechanical deposition greatly reduces the risk of hy-
B602Test Method for Attribute Sampling of Metallic and
drogen embrittlement and is suitable for coating bores and
Inorganic Coatings
recesses in many parts that cannot be conveniently plated
B697Guide for Selection of Sampling Plans for Inspection
electrolytically. (See Appendix X1.)
of Electrodeposited Metallic and Inorganic Coatings
1.3 The values stated in SI units are to be regarded as B762Test Method of Variables Sampling of Metallic and
Inorganic Coatings
standard. No other units of measurement are included in this
standard. E87MethodsforChemicalAnalysisofLead,Tin,Antimony,
and Their Alloys (Photometric Methods) (Withdrawn
1.4 This standard does not purport to address all of the
1983)
safety concerns, if any, associated with its use. It is the
E396Test Methods for Chemical Analysis of Cadmium
responsibility of the user of this standard to establish appro-
F1470Practice for Fastener Sampling for Specified Me-
priate safety and health practices and determine the applica-
chanical Properties and Performance Inspection
bilityofregulatorylimitationspriortouse.Forspecifichazards
statements, see Section 7. 2.2 U.S. Federal Standard:
FED-STD-141 Paint, Varnish, Lacquer, and Related Mate-
2. Referenced Documents
rials; Methods of Inspection, Sampling and Testing
2.1 ASTM Standards:
2.3 U.S. Military Standard:
B117Practice for Operating Salt Spray (Fog) Apparatus
MIL-L-7808JLubricatingOil,AircraftTurbineEngine,Syn-
B183Practice for Preparation of Low-Carbon Steel for
thetic Base
Electroplating
B201Practice for Testing Chromate Coatings on Zinc and
3. Classification
Cadmium Surfaces
3.1 Classes—Cadmium-tin coatings are classified on the
B242Guide for Preparation of High-Carbon Steel for Elec-
basis of thickness, as follows:
troplating
Class Minimum Thickness, µm
B322Guide for Cleaning Metals Prior to Electroplating
12 12
B487Test Method for Measurement of Metal and Oxide
Coating Thickness by Microscopical Examination of 55
Cross Section
3.2 Types—Cadmium-tincoatings areidentifiedbytypes on
B499Test Method for Measurement of CoatingThicknesses
the basis of supplementary treatment required, as follows:
3.2.1 Type I—As coated, without supplementary chromate
treatment (see X1.1).
This specification is under the jurisdiction of ASTM Committee B08 on
3.2.2 Type II—With supplementary chromate treatment (see
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
X1.2).
B08.06 on Soft Metals.
Current edition approved Sept. 1, 2009. Published November 2009. Originally
ε1
approved in 1978. Last previous edition approved in 2004 as B635–00(2004) .
DOI: 10.1520/B0635-00R09.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
the ASTM website. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
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B635−00(2009)
4. Ordering Information usedtoensureconformancetothesaltspraycorrosionresistant
requirements or to enhance the test results of the lead acetate
4.1 To make the application of this specification complete,
spot test (8.5.2).
the purchaser needs to supply the following information to the
supplier in the purchase order or other governing document:
5.3 Thickness:
4.1.1 Class, including a maximum thickness, if appropriate,
5.3.1 The thickness of the coating everywhere on the
type, and need for supplemental lubricant (3.1, 3.2, and
significant surfaces shall be at least that of the specified class
5.2.4.2).
as defined in 3.1.
4.1.2 Nature of substrate, for example, high-strength steel,
5.3.2 Significant surfaces are defined as those normally
need for stress-relief, and cleaning precautions to be followed
visible (directly or by reflection) that are essential to the
(5.2.2).
appearance or serviceability of the article when assembled in
4.1.3 Significant surfaces (5.3).
normal position; or which can be the source of corrosion
4.1.4 Requirements and methods of testing for one or more
products that deface visible surfaces on the assembled article.
of the following requirements: need for and type of test
When necessary, the significant surfaces shall be indicated on
specimens (8.1), composition (8.2), thickness (8.4), adhesion
the drawing of the article, or by the provision of suitably
(8.6), and absence of hydrogen embrittlement and the waiting
marked samples.
period prior to testing and testing loads (8.8) and lubricating
resistance (S2). NOTE1—Thethicknessofmechanically-depositedcoatingsvariesfrom
point-to-point on the surface of a product, characteristically tending to be
4.1.5 Sampling plan for each inspection criterion and re-
thicker on flat surfaces and thinner at exposed edges, sharp projections,
sponsibility for inspection, if necessary (Section 6 and Supple-
shielded or recessed areas, interior corners and holes, with such thinner
mentary Requirement S1).
areas often being exempted from thickness requirement.
4.1.6 Requirements for certified report of test results (Sec-
5.3.3 When significant surfaces are involved on which the
tion 10).
specified thickness of deposit cannot readily be controlled, the
purchaser and manufacturer should recognize the necessity for
5. Requirements
either thicker or thinner deposits. For example, to reduce
5.1 Nature of Finish—Thecoatingshallbe45to75mass%
buildup in thread roots, holes, deep recesses, bases of angles,
cadmium, the remainder tin.
and similar areas, the deposit thickness on the more accessible
5.2 Process:
surfaces will have to be reduced proportionately.
5.2.1 Stress Relief Treatment—All steel parts that have
NOTE 2—The coating thickness requirement of this specification is a
ultimate tensile strength of 1000 MPa and above and that
minimumrequirement;thatis,thecoatingthicknessisrequiredtoequalor
contain tensile stresses caused by machining, grinding,
exceed the specified thickness everywhere on the significant surfaces.
straightening, or cold forming operation shall be given a stress
Variation in the coating thickness from point to point on a coated article
relief heat treatment prior to cleaning and metal deposition.
is an inherent characteristic of mechanical deposition processes.
The temperature and time at temperature shall be 190 6 15°C Therefore, the coating thickness will have to exceed the specified value at
some points on the significant surfaces to ensure that the thickness equals
foraminimumof3hsothatmaximumstressreliefisobtained
or exceeds the specified value at all points. Thus, in most cases, the
without reducing the hardness below the specified minimum.
average coating thickness on an article will be greater than the specified
5.2.2 High-strength steels that have heavy oxide or scale
value; how much greater is largely determined by the shape of the article
shallbecleanedbeforeapplicationofthecoatinginaccordance
and the characteristics of the deposition process. In addition, the average
coating thickness on articles will vary from article to article within a
withGuideB242.Ingeneral,non-electrolyticalkaline,anodic-
production lot. Therefore, if all of the articles in a production lot are to
alkaline, and some inhibited acid cleaners are preferred to
meet the thickness requirement, the average coating thickness for the
avoid the risk of producing hydrogen embrittlement from the
production lot as a whole will be greater than the average necessary to
cleaning procedure.
ensure that a single article meets the requirement.
5.2.3 For preparation of low-carbon steels, see Practice
5.4 Adhesion—The cadmium-tin coating shall be suffi-
B183. For cleaning, useful guidelines are also given in Guide
ciently adherent to the basis metal to pass the tests specified in
B322.
8.6.
5.2.4 Supplementary Treatments:
5.2.4.1 Chromate treatment for Type II shall be done in a
5.5 Corrosion Resistance:
solution containing hexavalent chromium. This solution shall
5.5.1 The presence of corrosion products visible to the
produce a bright or semi-bright continuous, smooth, protective
unaided eye at normal reading distance at the end of the
film. This film may have a slight yellowish or iridescent color.
specifiedtestperiodasstatedinTable1shallconstitutefailure,
The absence of color shall not be considered evidence of the
except that corrosion products at the edges of specimens shall
absenceofaTypeIIfilmorasabasisforrejectionoftheparts.
not constitute failure. Slight “wisps” of white corrosion, as
Only post treatments that contain salts that yield films contain-
opposed to obvious accumulations, shall be acceptable.
ing hexavalent chromium are permitted as treatments for
NOTE 3—The hours given in Table 1 are the minimums required to
producing Type II coatings.
guaranteesatisfactoryperformance.Longerperiodsbeforetheappearance
5.2.4.2 Waxes, lacquers, or other organic coatings may be
of white corrosion products and rust are possible, but salt spray resistance
used to improve lubricity, and the need for them should be
does not vary in exact proportion with increased plating thickness. The
supplied in the purchase order or other governing document
hoursgivenforTypeIIreflecttheaddedprotectionofchromatetreatments
(4.1.1). Such supplemental lubrication treatments shall not be without requiring impractical testing periods.
B635−00(2009)
A
TABLE 1 Minimum Hours to Failure (White Corrosion and Red Rust for Cadmium-Tin Coatings on Iron and Steel)
Type Class 12 Class 8 Class 5
White Corrosion Rust White Corrosion Rust White Corrosion Rust
I not applicable 144 not applicable 120 not applicable 60
II 96 168 96 168 96 168
A
Corrosion products are those visible to the unaided eye at normal reading distances after gentle washing to remove salt deposits.
tropolishing. However, these are not normal in the treatment steps
5.5.2 Therearenorequirementsforcorrosionofbasemetals
preceding the application of the finish. When desired, they must be
other than steels.
specified on the purchase order (see 4.1.2).
NOTE 4—Mechanical deposition is exclusively a barrel-finishing pro-
cess. It is recognized that mechanical deposition on parts may therefore
6. Sampling
produce surfaces which have a different characteristic from those on parts
which are finished exclusively by racking. Similarly, corrosion testing of
6.1 The purchaser and producer are urged to employ statis-
actual parts may produce different results from those on test panels. Salt
tical process control in the coating process. Properly
spray requirements that are appropriate to indicate the technical quality
performed, statistical process control will assure coated prod-
with which a process is carried out may be impractical for acceptance of
ucts of satisfactory quality and will reduce the amount of
actual parts. In such cases the purchaser should indicate his requirements
acceptance inspection. The sampling plan used for the inspec-
on the purchase order (see 4.1.4).
NOTE 5—In many instances, there is no direct relation between the
tion of the quality coated article shall be agreed upon between
results of an accelerated corrosion test and the resistance to corrosion in
the purchaser and producer.
other media, because several factors that influence the progress of
6.1.1 When a collection of coated articles (inspection lot,
corrosion, such as the formation of protective films, vary greatly with the
see 6.2) is examined for compliance with the requirements
conditions encountered. The results obtained in the test should not,
therefore, be regarded as a direct guide to the corrosion resistance of the
placed on the articles, a relatively small number of the articles
tested materials in all environments where these materials may be used.
(sample)isselectedatrandomandisinspected.Theinspection
Also,performanceofdifferentmaterialsinthetestcannotalwaysbetaken
lot is then classified as complying with the requirements based
as a direct guide to the relative corrosion resistance of these materials in
on the results of the inspection of the sample. The size of the
service.
sample and the criteria for compliance are determined by the
5.6 AbsenceofHydrogenEmbrittlement—Steelspringsand
application of statistics. The procedure is known as sampling
other high-strength steel parts subject to flexure shall be held
inspection. Test Method B602, Guide B697, and Test Method
for a minimum of 48 h at room temperature after coating,
B762 contain sampling plans that are designed for sampling
before being loaded, flexed, or used. Such parts shall be free
inspection of coatings.
from hydrogen embrittlement. When specified in the purchase
6.1.2 TestMethodB602containsfoursamplingplans,three
order, freedom from embrittlement shall be determined by the
forusewithteststhatarenondestructiveandonewhentheyare
test specified herein (see 4.1.4 and 8.8).
destructive.TestMethodB602providesadefaultplanifoneis
5.7 Workmanship—The coating shall be uniform in appear-
not specified.
anceandsubstantiallyfreeofblisters,pits,nodules,flakingand
6.1.3 GuideB697providesalargenumberofplansandalso
other defects that can adversely affect the function of the
givesguidanceintheselectionofaplan.GuideB697provides
coating. The coating shall cover all surfaces as stated in 5.3,
a default plan if one is not specified.
including thread roots, thread peaks, corners, recesses, and
6.1.4 Test Method B762 can be used only for coating
edges. The coating shall not be stained or discolored through-
requirements that have a numerical limit, such as coating
out to an extent that would advers
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