ASTM B635-00(2023)
(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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements, see Section 7.
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: B635 − 00 (Reapproved 2023)
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.
1. Scope B322 Guide for Cleaning Metals Prior to Electroplating
B487 Test Method for Measurement of Metal and Oxide
1.1 This specification covers the requirements for a coating
Coating Thickness by Microscopical Examination of
that is a mixture of cadmium and tin mechanically deposited on
Cross Section
metal products. The coating is provided in various thicknesses
B499 Test Method for Measurement of Coating Thicknesses
up to and including 12 μm.
by the Magnetic Method: Nonmagnetic Coatings on
1.2 Mechanical deposition greatly reduces the risk of hy-
Magnetic Basis Metals
drogen embrittlement and is suitable for coating bores and
B567 Test Method for Measurement of Coating Thickness
recesses in many parts that cannot be conveniently plated
by the Beta Backscatter Method
electrolytically. (See Appendix X1.)
B571 Practice for Qualitative Adhesion Testing of Metallic
1.3 The values stated in SI units are to be regarded as Coatings
B602 Guide for Attribute Sampling of Metallic and Inor-
standard. No other units of measurement are included in this
standard. ganic Coatings
B697 Guide for Selection of Sampling Plans for Inspection
1.4 This standard does not purport to address all of the
of Electrodeposited Metallic and Inorganic Coatings
safety concerns, if any, associated with its use. It is the
B762 Guide of Variables Sampling of Metallic and Inorganic
responsibility of the user of this standard to establish appro-
Coatings
priate safety, health, and environmental practices and deter-
E87 Methods for Chemical Analysis of Lead, Tin, Antimony,
mine the applicability of regulatory limitations prior to use.
and Their Alloys (Photometric Methods) (Withdrawn
For specific hazards statements, see Section 7.
1983)
1.5 This international standard was developed in accor-
E396 Test Methods for Chemical Analysis of Cadmium
dance with internationally recognized principles on standard-
F1470 Practice for Fastener Sampling for Specified Me-
ization established in the Decision on Principles for the
chanical Properties and Performance Inspection
Development of International Standards, Guides and Recom-
2.2 U.S. Federal Standard:
mendations issued by the World Trade Organization Technical
FED-STD-141 Paint, Varnish, Lacquer, and Related Mate-
Barriers to Trade (TBT) Committee.
rials; Methods of Inspection, Sampling and Testing
2. Referenced Documents
2.3 U.S. Military Standard:
2.1 ASTM Standards:
MIL-L-7808J Lubricating Oil, Aircraft Turbine Engine, Syn-
B117 Practice for Operating Salt Spray (Fog) Apparatus
thetic Base
B183 Practice for Preparation of Low-Carbon Steel for
3. Classification
Electroplating
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
8 8
5 5
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
3.2 Types—Cadmium-tin coatings are identified by types on
B08.06 on Soft Metals.
the basis of supplementary treatment required, as follows:
Current edition approved May 1, 2023. Published June 2023. Originally
approved in 1978. Last previous edition approved in 2015 as B635 – 00 (2015).
DOI: 10.1520/B0635-00R23.
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 Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
the ASTM website. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B635 − 00 (2023)
3.2.1 Type I—As coated, without supplementary chromate ing hexavalent chromium are permitted as treatments for
treatment (see X1.1). producing Type II coatings.
3.2.2 Type II—With supplementary chromate treatment (see
5.2.4.2 Waxes, lacquers, or other organic coatings may be
X1.2).
used to improve lubricity, and the need for them should be
supplied in the purchase order or other governing document
4. Ordering Information
(4.1.1). Such supplemental lubrication treatments shall not be
used to ensure conformance to the salt spray corrosion resistant
4.1 To make the application of this specification complete,
requirements or to enhance the test results of the lead acetate
the purchaser needs to supply the following information to the
spot test (8.5.2).
supplier in the purchase order or other governing document:
4.1.1 Class, including a maximum thickness, if appropriate,
5.3 Thickness:
type, and need for supplemental lubricant (3.1, 3.2, and
5.3.1 The thickness of the coating everywhere on the
5.2.4.2).
significant surfaces shall be at least that of the specified class
4.1.2 Nature of substrate, for example, high-strength steel,
as defined in 3.1.
need for stress-relief, and cleaning precautions to be followed
5.3.2 Significant surfaces are defined as those normally
(5.2.2).
visible (directly or by reflection) that are essential to the
4.1.3 Significant surfaces (5.3).
appearance or serviceability of the article when assembled in
4.1.4 Requirements and methods of testing for one or more
normal position; or which can be the source of corrosion
of the following requirements: need for and type of test
products that deface visible surfaces on the assembled article.
specimens (8.1), composition (8.2), thickness (8.4), adhesion
When necessary, the significant surfaces shall be indicated on
(8.6), and absence of hydrogen embrittlement and the waiting
the drawing of the article, or by the provision of suitably
period prior to testing and testing loads (8.8) and lubricating
marked samples.
resistance (S2).
4.1.5 Sampling plan for each inspection criterion and re- NOTE 1—The thickness of mechanically-deposited coatings varies from
point-to-point on the surface of a product, characteristically tending to be
sponsibility for inspection, if necessary (Section 6 and Supple-
thicker on flat surfaces and thinner at exposed edges, sharp projections,
mentary Requirement S1).
shielded or recessed areas, interior corners and holes, with such thinner
4.1.6 Requirements for certified report of test results (Sec-
areas often being exempted from thickness requirement.
tion 10).
5.3.3 When significant surfaces are involved on which the
specified thickness of deposit cannot readily be controlled, the
5. Requirements
purchaser and manufacturer should recognize the necessity for
5.1 Nature of Finish—The coating shall be 45 to 75 mass %
either thicker or thinner deposits. For example, to reduce
cadmium, the remainder tin.
buildup in thread roots, holes, deep recesses, bases of angles,
5.2 Process:
and similar areas, the deposit thickness on the more accessible
5.2.1 Stress Relief Treatment—All steel parts that have
surfaces will have to be reduced proportionately.
ultimate tensile strength of 1000 MPa and above and that
NOTE 2—The coating thickness requirement of this specification is a
contain tensile stresses caused by machining, grinding,
minimum requirement; that is, the coating thickness is required to equal or
straightening, or cold forming operation shall be given a stress
exceed the specified thickness everywhere on the significant surfaces.
relief heat treatment prior to cleaning and metal deposition.
Variation in the coating thickness from point to point on a coated article
is an inherent characteristic of mechanical deposition processes.
The temperature and time at temperature shall be 190 °C 6
Therefore, the coating thickness will have to exceed the specified value at
15 °C for a minimum of 3 h so that maximum stress relief is
some points on the significant surfaces to ensure that the thickness equals
obtained without reducing the hardness below the specified
or exceeds the specified value at all points. Thus, in most cases, the
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
and the characteristics of the deposition process. In addition, the average
shall be cleaned before application of the coating in accordance
coating thickness on articles will vary from article to article within a
with Guide B242. In general, non-electrolytic alkaline, 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:
5.5 Corrosion Resistance:
5.2.4.1 Chromate treatment for Type II shall be done in a
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. specified test period as stated in Table 1 shall constitute failure,
The absence of color shall not be considered evidence of the except that corrosion products at the edges of specimens shall
absence of a Type II film or as a basis for rejection of the parts. 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.
B635 − 00 (2023)
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.
NOTE 3—The hours given in Table 1 are the minimums required to substrate over which they are applied is smooth and free of torn metal,
guarantee satisfactory performance. Longer periods before the appearance inclusions, pores, and other defects. It is recommended that the specifi-
of white corrosion products and rust are possible, but salt spray resistance cations covering the unfinished product provide limits for these defects. A
does not vary in exact proportion with increased plating thickness. The metal finisher can often remove defects through special treatments, such
hours given for Type II reflect the added protection of chromate treatments as grinding, polishing, abrasive blasting, chemical treatments, and elec-
without requiring impractical testing periods. tropolishing. However, these are not normal in the treatment steps
preceding the application of the finish. When desired, they must be
5.5.2 There are no requirements for corrosion of base metals
specified on the purchase order (see 4.1.2).
other than steels.
6. Sampling
NOTE 4—Mechanical deposition is exclusively a barrel-finishing pro-
cess. It is recognized that mechanical deposition on parts may therefore
6.1 The purchaser and producer are urged to employ statis-
produce surfaces which have a different characteristic from those on parts
tical process control in the coating process. Properly
which are finished exclusively by racking. Similarly, corrosion testing of
performed, statistical process control will assure coated prod-
actual parts may produce different results from those on test panels. Salt
ucts of satisfactory quality and will reduce the amount of
spray requirements that are appropriate to indicate the technical quality
with which a process is carried out may be impractical for acceptance of acceptance inspection. The sampling plan used for the inspec-
actual parts. In such cases the purchaser should indicate his requirements
tion of the quality coated article shall be agreed upon between
on the purchase order (see 4.1.4).
the purchaser and producer.
NOTE 5—In many instances, there is no direct relation between the
6.1.1 When a collection of coated articles (inspection lot,
results of an accelerated corrosion test and the resistance to corrosion in
see 6.2) is examined for compliance with the requirements
other media, because several factors that influence the progress of
corrosion, such as the formation of protective films, vary greatly with the placed on the articles, a relatively small number of the articles
conditions encountered. The results obtained in the test should not,
(sample) is selected at random and is inspected. The inspection
therefore, be regarded as a direct guide to the corrosion resistance of the
lot is then classified as complying with the requirements based
tested materials in all environments where these materials may be used.
on the results of the inspection of the sample. The size of the
Also, performance of different materials in the test cannot always be taken
sample and the criteria for compliance are determined by the
as a direct guide to the relative corrosion resistance of these materials in
service. application of statistics. The procedure is known as sampling
inspection. Test Method B602, Guide B697, and Test Method
5.6 Absence of Hydrogen Embrittlement—Steel springs and
B762 contain sampling plans that are designed for sampling
other high-strength steel parts subject to flexure shall be held
inspection of coatings.
for a minimum of 48 h at room t
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