ASTM B696-00(2023)

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, health, and environmental 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.  
1.7 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

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.06 - Soft Metals

Relations

• Refers: ASTM F1470-24 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 01-Jan-2024
• Refers: ASTM F1470-18 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 01-Feb-2018
• Refers: ASTM B183-79(2014) - Standard Practice for Preparation of Low-Carbon Steel for Electroplating
• Effective Date: 01-Nov-2014
• Refers: ASTM B242-99(2014) - Standard Guide for Preparation of High-Carbon Steel for Electroplating
• Effective Date: 01-Nov-2014
• Refers: ASTM F1470-12 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 15-Nov-2012
• Refers: ASTM B117-11 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Oct-2011
• Refers: ASTM B762-90(2010) - Standard Test Method of Variables Sampling of Metallic and Inorganic Coatings
• Effective Date: 01-Apr-2010
• Refers: ASTM B697-88(2010) - Standard Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
• Effective Date: 01-Apr-2010
• Refers: ASTM B602-88(2010) - Standard Test Method for Attribute Sampling of Metallic and Inorganic Coatings
• Effective Date: 01-Apr-2010
• Refers: ASTM B242-99(2009) - Standard Guide for Preparation of High-Carbon Steel for Electroplating
• Effective Date: 01-Sep-2009
• Refers: ASTM B322-99(2009) - Standard Guide for Cleaning Metals Prior to Electroplating
• Effective Date: 01-Sep-2009
• Refers: ASTM B567-98(2009a) - Standard Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
• Effective Date: 01-Sep-2009
• Refers: ASTM B183-79(2009) - Standard Practice for Preparation of Low-Carbon Steel for Electroplating
• Effective Date: 01-Sep-2009
• Refers: ASTM B117-09 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Jul-2009
• Refers: ASTM B567-98(2009) - Standard Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
• Effective Date: 15-Jun-2009

Overview

ASTM B696-00(2023) is the international standard specification for cadmium coatings mechanically deposited on metal products. Published by ASTM International, this standard establishes comprehensive requirements for the preparation, application, classification, and testing of mechanically deposited cadmium coatings. Mechanical deposition offers a viable alternative to electroplating, particularly for complex components and parts susceptible to hydrogen embrittlement, providing essential corrosion resistance and engineering properties.

Key applications of cadmium coatings include aerospace hardware, fasteners, electronic components, and other critical metal assemblies where corrosion protection and conductivity are important. The standard outlines classification based on thickness, supplementary treatments, and testing methods to ensure uniformity, quality, and safety of the coating.

Key Topics

• Coating Classifications

  • Class 12: 12 μm minimum thickness
  • Class 8: 8 μm minimum thickness
  • Class 5: 5 μm minimum thickness

• Coating Types

  • Type I: As-coated, no supplementary chromate treatment
  • Type II: Supplementary chromate conversion treatment for enhanced corrosion resistance and color identification

• Application and Process Guidelines

  • Mechanical deposition is ideal for coating bores, recesses, and features difficult to electroplate.
  • Process significantly reduces hydrogen embrittlement risk.
  • Requires meticulous surface preparation and, for high-strength steels, stress relief heat treatment prior to coating.

• Quality and Inspection

  • Coating must be uniform, free of blisters, flaking, pits, and other defects.
  • Thickness measured using recognized ASTM methods: microscopical, magnetic, and beta backscatter.
  • Coating must meet specified adhesion and corrosion resistance standards.
  • Corrosion resistance is validated through salt spray (fog) testing per ASTM B117.

• Safety and Health Considerations

  • Cadmium is toxic; coatings must not be used on food, beverage, or oral-contact articles.
  • Adequate ventilation is required during processes involving cadmium to manage harmful fumes, especially at temperatures above 320 °C.

Applications

Mechanically deposited cadmium coatings offer proven benefits in a variety of demanding environments:

• Aerospace and Defense: For components where reliability, corrosion resistance, and minimal risk of hydrogen embrittlement are critical.
• Fasteners and Connectors: Offers uniform protection on complex geometries, ensuring consistent performance in challenging conditions.
• Electronics and Engineering: Enhances conductivity and resists corrosion, extending the service life of parts.
• Automotive and Industrial: Protects vulnerable parts in harsh environments, reducing maintenance frequency and costs.

These coatings are especially advantageous for parts with bores, threads, and recesses that are hard to access with electroplating methods. The mechanical process ensures a thorough and consistent application without inducing hydrogen embrittlement, a significant issue for high-strength steel parts.

Related Standards

To ensure quality and consistency, ASTM B696-00(2023) references and works alongside numerous related ASTM standards, including:

• ASTM B117: Salt Spray (Fog) Testing for corrosion resistance
• ASTM B183: Preparation of Low-Carbon Steel for Electroplating
• ASTM B242: Preparation of High-Carbon Steel for Electroplating
• ASTM B322: Cleaning Metals Prior to Electroplating
• ASTM B487, B499, B567: Measurement of coating thickness
• ASTM B602, B697, B762, F1470: Sampling and inspection methods

These interrelated standards help producers and purchasers specify, measure, and assure the performance of mechanically deposited cadmium coatings across industries.

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ASTM B696-00(2023) cadmium coating standard helps organizations achieve durable, high-quality corrosion protection for metal components, while focusing on safety, environmental, and quality requirements in accordance with internationally recognized best practices.

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: B696 − 00 (Reapproved 2023)
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 U.S. Department of Defense.
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.
1.7 This international standard was developed in accor-
1.2 Mechanical deposition greatly reduces the risk of hy- dance with internationally recognized principles on standard-
drogen embrittlement and is suitable for coating bores and ization established in the Decision on Principles for the
recesses in many parts that cannot be conveniently electro-
Development of International Standards, Guides and Recom-
plated (see Appendix X3).
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.3 Cadmium coatings are usually applied to provide engi-
neering properties and corrosion resistance. The performance
2. Referenced Documents
of a cadmium coating depends largely on its thickness and the
kind of environment to which it is exposed. Without proof of 2
2.1 ASTM Standards:
satisfactory correlation, accelerated tests such as the salt spray
B117 Practice for Operating Salt Spray (Fog) Apparatus
(fog) test cannot be relied upon to predict performance in other
B183 Practice for Preparation of Low-Carbon Steel for
environments, nor will these serve as comparative measures of
Electroplating
the corrosion resistance afforded by coatings of different
B242 Guide for Preparation of High-Carbon Steel for Elec-
metals. Thus, although there is a marked superiority of cad-
troplating
mium coatings over zinc coatings of equal thickness in the salt
B322 Guide for Cleaning Metals Prior to Electroplating
spray test, this is often not the case under conditions of use, so
B487 Test Method for Measurement of Metal and Oxide
that further testing in the service environment should be
Coating Thickness by Microscopical Examination of
conducted.
Cross Section
1.4 This standard does not purport to address all of the
B499 Test Method for Measurement of Coating Thicknesses
safety concerns, if any, associated with its use. It is the
by the Magnetic Method: Nonmagnetic Coatings on
responsibility of the user of this standard to establish appro-
Magnetic Basis Metals
priate safety, health, and environmental practices and deter-
B567 Test Method for Measurement of Coating Thickness
mine the applicability of regulatory limitations prior to use.
by the Beta Backscatter Method
For specific precautionary statements, see 1.5 and 1.6.
B602 Guide for Attribute Sampling of Metallic and Inor-
1.5 Warning—Cadmium is toxic and must not be used in a
ganic Coatings
coating for articles that can come into contact with food or
B697 Guide for Selection of Sampling Plans for Inspection
beverages, or for dental or other equipment that can be inserted
of Electrodeposited Metallic and Inorganic Coatings
into the mouth. Consult appropriate agencies for regulations in
B762 Guide of Variables Sampling of Metallic and Inorganic
this connection.
Coatings
1.6 Warning—Because of the toxicity of cadmium vapors
F1470 Practice for Fastener Sampling for Specified Me-
and cadmium oxide fumes, cadmium-coated articles must not
chanical Properties and Performance Inspection
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and 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 May 1, 2023. Published June 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1981. Last previous edition approved in 2015 as B696 – 00 (2015). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/B0696-00R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B696 − 00 (2023)
3. Classification 6.2.1 Stress-Relief Treatment—All steel parts that have ul-
timate tensile strength of 1000 MPa and above and that contain
3.1 Classes—Cadmium coatings are classified on the basis
tensile stresses caused by machining, grinding, straightening,
of thickness, as follows:
or cold-forming operation shall be given a stress relief heat
Class Minimum Thickness, μm
treatment prior to cleaning and metal deposition. The tempera-
12 12
8 8 ture and time at temperature shall be 190 °C 6 15 °C for a
5 5
minimum of 3 h so that maximum stress relief is obtained
3.2 Types—Cadmium coatings are identified by types on the without reducing the hardness below the specified minimum.
basis of supplementary treatment required, as follows: 6.2.2 High-strength steels that have heavy oxide or scale
Type I—As coated without supplementary chromate treat- shall be cleaned before application of the coating in accordance
ment (Appendix X2.1). with Practice B242. In general, nonelectrolytic alkaline,
Type II—With colored chromate conversion treatment (Ap- anodic-alkaline, and some inhibited acid cleaners are preferred
to avoid the risk of producing hydrogen embrittlement from the
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.
4.1 To make the application of this standard complete, the
6.2.4 Supplementary Treatments:
purchaser should supply the following information to the seller
6.2.4.1 Colored Chromate Conversion Treatments (Type
in the purchase order or other governing document:
II)—Chromate treatment for Type II shall be done in a solution
4.1.1 Class, including a maximum thickness, if appropriate,
containing hexavalent chromium. This solution shall produce a
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
4.1.2 Nature of substrate (for example, high-strength steel),
and olive drab to brown and black including olive drab and that
needed for stress relief (6.2.1), and cleaning precautions to be
may be dyed to a desired color. Post treatments that do not
followed 6.2.2 and 6.2.3),
contain salts that yield films containing hexavalent chromium
4.1.3 Significant surfaces (6.3),
are not permitted as treatments for producing Type 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). Supplemental lubrication treatment shall not be used to
embrittlement, and the waiting period before testing and testing
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, roll marks, inclusions, and so forth)
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-
cations covering the unfinished product provide limits for these defects. 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
not be stained or discolored throughout to an extent that would 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
normal position; or that can be the source of corrosion products
6. Requirements
that deface visible surfaces on the assembled article. When
necessary, the significant surfaces shall be indicated on the
6.1 Appearance—The coating as deposited shall have a
drawing for the article, or by the provision of suitably marked
uniform silvery appearance, and a matte to medium-bright
samples.
luster.
6.2 Process: NOTE 3—The thickness of mechanically-deposited coatings varies from
B696 − 00 (2023)
point-to-point on the surface of a product, characteristically tending to be with which a process is carried out may be impractical for acceptance of
thicker on flat surfaces and thinner at exposed edges, sharp projections, actual parts. In such cases the purchaser should indicate his requirements
shielded or recessed areas, interior corners and holes, with such thinner
on the purchaser order (4.1.4).
areas often being exempted from thickness requirements.
NOTE 7—In many instances, there is no direct relation between the
results of an accelerated corrosion test and the resistance to corrosion in
6.3.3 When significant surfaces are involved on which the
other media, because several factors that influence the progress of
specified thickness of deposit cannot readily be controlled, the
corrosion, such as the formation of protective films, vary greatly with the
purchaser and manufacturer should recognize the necessity for
conditions encountered. The results obtained in the test should not,
either thicker or thinner deposits. For example, to reduce
therefore, be regarded as a direct guide to the corrosion resistance of the
buildup in thread roots, holes, deep recesses, bases of angles, tested materials in all environments where these materials may be used.
Also, performance of different materials in the test cannot always be taken
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
minimum requirement; that is, the coating thickness is required to equal or
hours for either white corrosion products or rust shall apply.
exceed the specified thickness everywhere on the significant surfaces.
Variation in the coating thickness from point to point on a coated article
For example, for Type II, Class 5, the test shall be continued
is an inherent characteristic of mechanical deposition processes.
until the 72 h requirement is met for white corrosion products;
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
average coating thickness on an article will be greater than the specified
requirement for basis metal corrosion is met (8.5.2).
value; how much greater is largely determined by the shape of the article
and the characteristics of the deposition process. In addition, the average 6.6 Absence of Hydrogen Embrittlement—Steel springs and
coating thickness on articles will vary from article to article within a
other high-strength steel parts subject to flexure shall be held
production lot. Therefore, if all of the articles in a production lot are to
for a minimum of 48 h at room temperature after coating before
meet the thickness requirement, the average coating thickness for the
being loaded, flexed, or used. Such high-strength steel parts
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.
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
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
NOTE 5—The hours given in Table 1 are the minimums required to
the purchaser and producer.
guarantee satisfactory performance. Longer periods before the appearance
of white corrosion products and rust are possible, but salt spray resistance 7.1.1 When a collection of coated articles (inspection lot,
does not vary in exact proportion with increased plating thickness. The
see 7.2) is examined for compliance with the requirements
hours given for Type II reflect the added protection of chromate treatments
placed on the articles, a relatively small number of the articles
without requiring impractical tes
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