ASTM B635-00(2004)e1
(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 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 plated electrolytically. (See Appendix X1.)
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. For specific hazards statements, see Section 7.
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Designation: B635 – 00 (Reapproved 2004)
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Updated warning note in 7.2 and added keywords editorially in August 2004.
1. Scope by the Beta Backscatter Method
B571 Practice for Qualitative Adhesion Testing of Metallic
1.1 This specification covers the requirements for a coating
Coatings
thatisamixtureofcadmiumandtinmechanicallydepositedon
B602 Test Method for Attribute Sampling of Metallic and
metal products. The coating is provided in various thicknesses
Inorganic Coatings
up to and including 12 µm.
B697 Guide for Selection of Sampling Plans for Inspection
1.2 Mechanical deposition greatly reduces the risk of hy-
of Electrodeposited Metallic and Inorganic Coatings
drogen embrittlement and is suitable for coating bores and
B762 Test Method of Variables Sampling of Metallic and
recesses in many parts that cannot be conveniently plated
Inorganic Coatings
electrolytically. (See Appendix X1.)
E87 Methods for Chemical Analysis of Lead, Tin, Anti-
1.3 This standard does not purport to address all of the
mony, and Their Alloys (Photometric Methods)
safety concerns, if any, associated with its use. It is the
E396 Test Methods for Chemical Analysis of Cadmium
responsibility of the user of this standard to establish appro-
F1470 Practice for Fastener Sampling for Specified Me-
priate safety and health practices and determine the applica-
chanical Properties and Performance Inspection
bilityofregulatorylimitationspriortouse.Forspecifichazards
2.2 U.S. Federal Standard:
statements, see Section 7.
FED-STD-141 Paint, Varnish, Lacquer, and Related Mate-
2. Referenced Documents
rials; Methods of Inspection, Sampling and Testing
2.3 U.S. Military Standard:
2.1 ASTM Standards:
MIL-L-7808J Lubricating Oil, Aircraft Turbine Engine,
B117 Practice for Operating Salt Spray (Fog) Apparatus
Synthetic Base
B183 Practice for Preparation of Low-Carbon Steel for
Electroplating
3. Classification
B201 Practice for Testing Chromate Coatings on Zinc and
3.1 Classes—Cadmium-tin coatings are classified on the
Cadmium Surfaces
basis of thickness, as follows:
B242 Guide for Preparation of High-Carbon Steel for Elec-
Class Minimum Thickness, µm
troplating
12 12
B322 Guide for Cleaning Metals Prior to Electroplating
B487 Test Method for Measurement of Metal and Oxide
CoatingThicknessbyMicroscopicalExaminationofCross
3.2 Types—Cadmium-tin coatings are identified by types on
Section
the basis of supplementary treatment required, as follows:
B499 Test Method for Measurement of Coating Thick-
3.2.1 Type I—As coated, without supplementary chromate
nessesbytheMagneticMethod:NonmagneticCoatingson
treatment (see X1.1).
Magnetic Basis Metals
3.2.2 Type II—With supplementary chromate treatment (see
B567 Test Method for Measurement of Coating Thickness
X1.2).
4. Ordering Information
This specification is under the jurisdiction of ASTM Committee B08 on
4.1 To make the application of this specification complete,
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.08.04 on Soft Metals. the purchaser needs to supply the following information to the
Current edition approved Aug. 1, 2004. Published August 2004. Originally
supplier in the purchase order or other governing document:
approved in 1978. Last previous edition approved in 2000 as B635 – 00. DOI:
10.1520/B0635-00R04E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Withdrawn.
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.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
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B635 – 00 (2004)
4.1.1 Class, including a maximum thickness, if appropriate, supplied in the purchase order or other governing document
type, and need for supplemental lubricant (3.1, 3.2, and (4.1.1). Such supplemental lubrication treatments shall not be
5.2.4.2). usedtoensureconformancetothesaltspraycorrosionresistant
4.1.2 Nature of substrate, for example, high-strength steel, requirements or to enhance the test results of the lead acetate
need for stress-relief, and cleaning precautions to be followed spot test (8.5.2).
(5.2.2). 5.3 Thickness:
4.1.3 Significant surfaces (5.3). 5.3.1 The thickness of the coating everywhere on the
4.1.4 Requirements and methods of testing for one or more significant surfaces shall be at least that of the specified class
of the following requirements: need for and type of test as defined in 3.1.
specimens (8.1), composition (8.2), thickness (8.4), adhesion 5.3.2 Significant surfaces are defined as those normally
(8.6), and absence of hydrogen embrittlement and the waiting visible (directly or by reflection) that are essential to the
period prior to testing and testing loads (8.8) and lubricating appearance or serviceability of the article when assembled in
resistance (S2). normal position; or which can be the source of corrosion
4.1.5 Sampling plan for each inspection criterion and re- products that deface visible surfaces on the assembled article.
sponsibility for inspection, if necessary (Section 6 and Supple- When necessary, the significant surfaces shall be indicated on
mentary Requirement S1). the drawing of the article, or by the provision of suitably
4.1.6 Requirements for certified report of test results (Sec- marked samples.
tion 10).
NOTE 1—Thethicknessofmechanically-depositedcoatingsvariesfrom
point-to-point on the surface of a product, characteristically tending to be
5. Requirements
thicker on flat surfaces and thinner at exposed edges, sharp projections,
5.1 NatureofFinish—The coating shall be 45 to 75 mass % shielded or recessed areas, interior corners and holes, with such thinner
areas often being exempted from thickness requirement.
cadmium, the remainder tin.
5.2 Process:
5.3.3 When significant surfaces are involved on which the
5.2.1 Stress Relief Treatment—All steel parts that have
specified thickness of deposit cannot readily be controlled, the
ultimate tensile strength of 1000 MPa and above and that
purchaser and manufacturer should recognize the necessity for
contain tensile stresses caused by machining, grinding,
either thicker or thinner deposits. For example, to reduce
straightening, or cold forming operation shall be given a stress
buildup in thread roots, holes, deep recesses, bases of angles,
relief heat treatment prior to cleaning and metal deposition.
and similar areas, the deposit thickness on the more accessible
The temperature and time at temperature shall be 190 6 15°C
surfaces will have to be reduced proportionately.
for a minimum of3hso that maximum stress relief is obtained
NOTE 2—The coating thickness requirement of this specification is a
without reducing the hardness below the specified minimum.
minimumrequirement;thatis,thecoatingthicknessisrequiredtoequalor
5.2.2 High-strength steels that have heavy oxide or scale
exceed the specified thickness everywhere on the significant surfaces.
shallbecleanedbeforeapplicationofthecoatinginaccordance
Variation in the coating thickness from point to point on a coated article
with Guide B242. In general, non-electrolytic alkaline, anodic-
is an inherent characteristic of mechanical deposition processes. There-
alkaline, and some inhibited acid cleaners are preferred to fore, the coating thickness will have to exceed the specified value at some
points on the significant surfaces to ensure that the thickness equals or
avoid the risk of producing hydrogen embrittlement from the
exceeds the specified value at all points. Thus, in most cases, the average
cleaning procedure.
coating thickness on an article will be greater than the specified value;
5.2.3 For preparation of low-carbon steels, see Practice
how much greater is largely determined by the shape of the article and the
B183. For cleaning, useful guidelines are also given in Guide
characteristics of the deposition process. In addition, the average coating
B322.
thickness on articles will vary from article to article within a production
5.2.4 Supplementary Treatments:
lot. Therefore, if all of the articles in a production lot are to meet the
5.2.4.1 Chromate treatment for Type II shall be done in a thicknessrequirement,theaveragecoatingthicknessfortheproductionlot
as a whole will be greater than the average necessary to ensure that a
solution containing hexavalent chromium. This solution shall
single article meets the requirement.
produce a bright or semi-bright continuous, smooth, protective
film. This film may have a slight yellowish or iridescent color. 5.4 Adhesion—The cadmium-tin coating shall be suffi-
The absence of color shall not be considered evidence of the ciently adherent to the basis metal to pass the tests specified in
absence of aType II film or as a basis for rejection of the parts. 8.6.
Only post treatments that contain salts that yield films contain- 5.5 Corrosion Resistance:
ing hexavalent chromium are permitted as treatments for 5.5.1 The presence of corrosion products visible to the
producing Type II coatings. unaided eye at normal reading distance at the end of the
5.2.4.2 Waxes, lacquers, or other organic coatings may be specified test period as stated inTable 1 shall constitute failure,
used to improve lubricity, and the need for them should be except that corrosion products at the edges of specimens shall
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.
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B635 – 00 (2004)
tropolishing. However, these are not normal in the treatment steps
not constitute failure. Slight “wisps” of white corrosion, as
preceding the application of the finish. When desired, they must be
opposed to obvious accumulations, shall be acceptable.
specified on the purchase order (see 4.1.2).
NOTE 3—The hours given in Table 1 are the minimums required to
guarantee satisfactory performance. Longer periods before the appearance 6. Sampling
of white corrosion products and rust are possible, but salt spray resistance
6.1 The purchaser and producer are urged to employ statis-
does not vary in exact proportion with increased plating thickness. The
tical process control in the coating process. Properly per-
hoursgivenforTypeIIreflecttheaddedprotectionofchromatetreatments
formed, statistical process control will assure coated products
without requiring impractical testing periods.
of satisfactory quality and will reduce the amount of accep-
5.5.2 Therearenorequirementsforcorrosionofbasemetals
tance inspection. The sampling plan used for the inspection of
other than steels.
the quality coated article shall be agreed upon between the
NOTE 4—Mechanical deposition is exclusively a barrel-finishing pro-
purchaser and producer.
cess. It is recognized that mechanical deposition on parts may therefore
6.1.1 When a collection of coated articles (inspection lot,
produce surfaces which have a different characteristic from those on parts
see 6.2) is examined for compliance with the requirements
which are finished exclusively by racking. Similarly, corrosion testing of
placed on the articles, a relatively small number of the articles
actual parts may produce different results from those on test panels. Salt
(sample) is selected at random and is inspected.The inspection
spray requirements that are appropriate to indicate the technical quality
lot is then classified as complying with the requirements based
with which a process is carried out may be impractical for acceptance of
on the results of the inspection of the sample. The size of the
actual parts. In such cases the purchaser should indicate his requirements
on the purchase order (see 4.1.4).
sample and the criteria for compliance are determined by the
NOTE 5—In many instances, there is no direct relation between the
application of statistics. The procedure is known as sampling
results of an accelerated corrosion test and the resistance to corrosion in
inspection. Test Method B602, Guide B697, and Test Method
other media, because several factors that influence the progress of
B762 contain sampling plans that are designed for sampling
corrosion, such as the formation of protective films, vary greatly with the
inspection of coatings.
conditions encountered. The results obtained in the test should not,
6.1.2 Test Method B602 contains four sampling plans, three
therefore, be regarded as a direct guide to the corrosion resistance of the
tested materials in all environments where these materials may be used. forusewithteststhatarenondestructiveandonewhentheyare
Also,performanceofdifferentmaterialsinthetestcannotalwaysbetaken
destructive.Test Method B602 provides a default plan if one is
as a direct guide to the relative corrosion resistance of these materials in
not specified.
service.
6.1.3 Guide B697 provides a large number of plans and also
5.6 AbsenceofHydrogenEmbrittlement—Steelspringsand gives guidance in the selection of a plan. Guide B697 provides
other high-strength steel parts subject to flexure shall be held a default plan if one is not specified.
for a minimum of 48 h at room temperature after coating,
6.1.4 Test Method B762 can be used only for coating
before being loaded, flexed, or used. Such parts shall be free requirements that have a numerical limit, such as coating
from hydrogen embrittlement. When specified in the purchase
thickness. The test must yield a numeric value and certain
order, freedom from embrittlement shall be determined by the statistical requirements must be met. Test Method B762
test specified herein (see 4.1.4 and 8.8). contains several plans and also gives instructions for calculat-
5.7 Workmanship—The coating shall be uniform in appear- ing plans to meet special needs. Test Method B762 provides a
anceandsubstantiallyfreeofblisters,pits,nodules,flakingand default plan if one is not specified.
other defec
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