ASTM B696-00(2015)
(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 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 and health 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.
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Designation: B696 − 00 (Reapproved 2015)
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.
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
Coating Thickness by Microscopical Examination of
(fog) test cannot be relied upon to predict performance in other
Cross Section
environments, nor will these serve as comparative measures of
B499 Test Method for Measurement of Coating Thicknesses
the corrosion resistance afforded by coatings of different
by the Magnetic Method: Nonmagnetic Coatings on
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
B762 Test Method of Variables Sampling of Metallic and
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- Inorganic Coatings
F1470 Practice for Fastener Sampling for Specified Me-
bility of regulatory limitations prior to use. For specific
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
3. Classification
coating for articles that can come into contact with food or
beverages, or for dental or other equipment that can be inserted
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
12 12
1.6 Warning—Because of the toxicity of cadmium vapors
8 8
and cadmium oxide fumes, cadmium-coated articles must not
5 5
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 March 1, 2015. Published April 2015. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1981. Last previous edition approved in 2009 as B696 – 00(2009). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0696-00R15. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B696 − 00 (2015)
3.2 Types—Cadmium coatings are identified by types on the 6.2.2 High-strength steels that have heavy oxide or scale
basis of supplementary treatment required, as follows: shall be cleaned before application of the coating in accordance
Type I—As coated without supplementary chromate treat- with Practice B242. In general, nonelectrolytic alkaline,
ment (Appendix X2.1). anodic-alkaline, and some inhibited acid cleaners are preferred
Type II—With colored chromate conversion treatment (Ap- 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.
6.2.4 Supplementary Treatments:
4.1 To make the application of this standard complete, the
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
a uniform color that may range from yellow through bronze
lubricant (see 3.1, 3.2, and 6.2.4.2),
4.1.2 Nature of substrate (for example, high-strength steel), and olive drab to brown and black including olive drab and that
may be dyed to a desired color. Post treatments that do not
needed for stress relief (6.2.1), and cleaning precautions to be
followed 6.2.2 and 6.2.3), contain salts that yield films containing hexavalent chromium
are not permitted as treatments for producing Type II coatings.
4.1.3 Significant surfaces (6.3),
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.
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
normal position; or that can be the source of corrosion products
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:
NOTE 3—The thickness of mechanically-deposited coatings varies from
6.2.1 Stress-Relief Treatment—All steel parts that have ul-
point-to-point on the surface of a product, characteristically tending to be
timate tensile strength of 1000 MPa and above and that contain thicker on flat surfaces and thinner at exposed edges, sharp projections,
shielded or recessed areas, interior corners and holes, with such thinner
tensile stresses caused by machining, grinding, straightening,
areas often being exempted from thickness requirements.
or cold-forming operation shall be given a stress relief heat
treatment prior to cleaning and metal deposition. The tempera- 6.3.3 When significant surfaces are involved on which the
ture and time at temperature shall be 190 6 15°C for a specified thickness of deposit cannot readily be controlled, the
minimum of 3 h so that maximum stress relief is obtained purchaser and manufacturer should recognize the necessity for
without reducing the hardness below the specified minimum. either thicker or thinner deposits. For example, to reduce
B696 − 00 (2015)
tested materials in all environments where these materials may be used.
buildup in thread roots, holes, deep recesses, bases of angles,
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.
For example, for Type II, Class 5, the test shall be continued
Variation in the coating thickness from point to point on a coated article
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
requirement for basis metal corrosion is met (8.5.2).
average coating thickness on an article will be greater than the specified
value; how much greater is largely determined by the shape of the article
6.6 Absence of Hydrogen Embrittlement—Steel springs and
and the characteristics of the deposition process. In addition, the average
other high-strength steel parts subject to flexure shall be held
coating thickness on articles will vary from article to article within a
for a minimum of 48 h at room temperature after coating before
production lot. Therefore, if all of the articles in a production lot are to
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.
7. Sampling
6.5 Corrosion Resistance:
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
the purchaser and producer.
NOTE 5—The hours given in Table 1 are the minimums required to
7.1.1 When a collection of coated articles (inspection lot,
guarantee satisfactory performance. Longer periods before the appearance
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
hours given for Type II reflect the added protection of chromate treatments
(sample) is selected at random and is inspected. The inspection
without requiring impractical testing periods.
lot is then classified as complying with the requirements based
6.5.2 There are no requirements for corrosion of bas
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B696 − 00 (Reapproved 2009) B696 − 00 (Reapproved 2015)
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
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 and health 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.
2. Referenced Documents
2.1 ASTM Standards:
B117 Practice for Operating Salt Spray (Fog) Apparatus
B183 Practice for Preparation of Low-Carbon Steel for Electroplating
B242 Guide for Preparation of High-Carbon Steel for Electroplating
B322 Guide for Cleaning Metals Prior to Electroplating
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis
Metals
B567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
F1470 Practice for Fastener Sampling for Specified Mechanical 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.
Current edition approved Sept. 1, 2009March 1, 2015. Published December 2009April 2015. Originally approved in 1981. Last previous edition approved in 20042009
ε1
as B696 – 00(2004)(2009). . DOI: 10.1520/B0696-00R09.10.1520/B0696-00R15.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B696 − 00 (2015)
3. Classification
3.1 Classes—Cadmium coatings are classified on the basis of thickness, as follows:
Class Minimum Thickness, μm
12 12
8 8
5 5
3.2 Types—Cadmium coatings are identified by types on the basis of supplementary treatment required, as follows:
Type I—As coated without supplementary chromate treatment (Appendix X2.1).
Type II—With colored chromate conversion treatment (Appendix X2.2).
4. Ordering Information
4.1 To make the application of this standard complete, the purchaser should supply the following information to the seller in
the purchase order or other governing document:
4.1.1 Class, including a maximum thickness, if appropriate, Type, and for Type II, color and need for supplemental lubricant
(see 3.1, 3.2, and 6.2.4.2),
4.1.2 Nature of substrate (for example, high-strength steel), needed for stress relief (6.2.1), and cleaning precautions to be
followed 6.2.2 and 6.2.3),
4.1.3 Significant surfaces (6.3),
4.1.4 Requirements for and methods of testing for one or more of the following, if required: need for and type of test specimens
(8.1), thickness (6.3 and 8.3), adhesion (6.4 and 8.4), corrosion resistance (6.5 and 8.5), absence of hydrogen embrittlement, and
the waiting period before testing and testing loads (6.6 and 8.6),
4.1.5 Inspection responsibility (Supplementary Requirement S1) and sampling plan for each inspection criterion (Section 7).
4.1.6 Requirements for certified report of test results (Section 10).
5. Workmanship
5.1 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. The coating shall cover all surfaces as stated in 6.3 including roots of threads, thread peaks,
corners, recesses, and edges. The coating shall not be stained or discolored throughout to an extent that would adversely affect
appearance as a functional requirement. However, superficial staining that results from rinsing or drying and variations in color
or luster shall not be cause for rejection.
NOTE 1—The nature of the mechanical plating process is such that coatings characteristically will not be as smooth or as bright as some electroplated
coatings.
6. Requirements
6.1 Appearance—The coating as deposited shall have a uniform silvery appearance, and a matte to medium-bright luster.
6.2 Process:
6.2.1 Stress-Relief Treatment—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. The temperature and time at temperature shall be 190 6 15°C for a minimum of 3 h so that
maximum stress relief is obtained without reducing the hardness below the specified minimum.
6.2.2 High-strength steels that have heavy oxide or scale shall be cleaned before application of the coating in accordance with
Practice B242. In general, nonelectrolytic alkaline, anodic-alkaline, and some inhibited acid cleaners are preferred to avoid the risk
of producing hydrogen embrittlement from the cleaning procedure.
6.2.3 For low-carbon steels see Practice B183. Useful guidelines are also given in Practice B322.
6.2.4 Supplementary Treatments:
6.2.4.1 Colored Chromate Conversion Treatments (Type II)—Chromate treatment for Type II shall be done in a solution
containing hexavalent chromium. This solution shall produce a bright or semi-bright continuous, smooth, protective film with a
uniform color that may range from yellow through bronze and olive drab to brown and black including olive drab and that may
be dyed to a desired color. Post treatments that do not contain salts that yield films containing hexavalent chromium are not
permitted as treatments for producing Type II coatings.
6.2.4.2 Waxes, lacquers, or other organic coatings may be used to improve lubricity, and the need for them shall be supplied
in the purchase order or other governing document (4.1.1). Supplemental lubrication treatment shall not be used to ensure
conformance to the salt spray corrosion resistance requirements.
6.2.5 Surface Defects—Defects and variations in appearance in the coating that arise from surface conditions of the substrate
(scratches, pores, roll marks, inclusions, and so forth) and that persist in the finish despite the observance of good metal finishing
practices shall not be cause for rejection.
NOTE 2—Applied finishes generally perform better in service when the substrate over which they are applied is smooth and free of torn metal,
B696 − 00 (2015)
inclusions, pores, and other defects. It is recommended that the specifications covering the unfinished product provide limits for these defects. A metal
finisher can often remove defects through special treatments, such as grinding, polishing, abrasive blasting, chemical treatments, and electropolishing.
However, these are not normal in the treatment steps preceding the application of the finish. When desired they must be specified on the purchase order
(4.1.2).
6.3 Thickness:
6.3.1 The thickness of the coating everywhere on the significant surfaces shall be at least that of the specified class as defined
in 3.1.
6.3.2 Significant surfaces are defined as those normally visible (directly or by reflection) that are essential to the appearance or
serviceability of the article when assembled in normal position; or that can be the source of corrosion products that deface visible
surfaces on the assembled article. When necessary, the significant surfaces shall be indicated on the drawing for the article, or by
the provision of suitably marked samples.
NOTE 3—The thickness of mechanically-deposited coatings varies from point-to-point on the surface of a product, characteristically tending to be
thicker on flat surfaces and thinner at exposed edges, sharp projections, shielded or recessed areas, interior corners and holes, with such thinner areas often
being exempted from thickness requirements.
6.3.3 When significant surfaces are involved on which the specified thickness of deposit cannot readily be controlled, the
purchaser and manufacturer should recognize the necessity for either thicker or thinner deposits. For example, to reduce buildup
in thread roots, holes, deep recesses, bases of angles, and similar areas, the deposit thickness on the more accessible surfaces will
have to be reduced proportionately.
NOTE 4—The coating thickness requirement of this specification is a minimum requirement; that is, the coating thickness is required to equal or exceed
the specified thickness everywhere on the significant surfaces. Variation in the coating thickness from point to point on a coated article is an inherent
characteristic of mechanical deposition processes. Therefore, the coating thickness will have to exceed the specified value at some points on the significant
surfaces to ensure that the thickness equals 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 value; how much greater is largely determined by the shape of the article and the characteristics of the deposition process.
In addition, the average coating thickness on articles will vary from article to article within a production lot. Therefore, if all of the articles in a production
lot are to meet the thickness requirement, the average coating thickness for the production lot as a whole will be greater than the average necessary to
ensure that a single article meets the requirement.
6.4 Adhesion—The cadmium coating shall be sufficiently adherent to the basis metal to pass the tests specified in 8.4.
6.5 Corrosion Resistance:
6.5.1 The presence of corrosion products visible to the unaided eye at normal reading distance at the end of the specified test
periods stated in Table 1 shall constitute failure, except that corrosion products at edges of specimens shall not constitute failure.
Slight “wisps” of white corrosion, as opposed to obvious accumulations, shall be acceptable.
NOTE 5—The hours given in Table 1 are the minimums required to guarantee satisfactory performance. Longer periods before the appearance of white
corrosion products and rust are possible, but salt spray resistance does not vary in exact proportion with increased plating thickness. The hours given for
Type II reflect the added protection of chromate treatments without requiring impractical testing periods.
6.5.2 There are no requirements for corrosion of basis metals other than steels.
NOTE 6—Mechanical deposition is exclusively a barrel-finishing process. It is recognized that mechanical deposition on parts may therefore produce
surfaces that have a different characteristic from those on parts that are finished exclusively by racking. Similarly, corrosion testing of actual parts may
produce different results from those on test panels. Salt spray requirements that are appropriate to indicate the technical quality with which a process is
carried out may be impractical for acceptance of actual parts. In such cases the purchaser should indicate his requirements on the purchaser order (4.1.4).
NOTE 7—In many instances, there is no direct relation between the results of an accelerated corrosion test and the resistance to corrosion in other media,
because several factors that influence the progress of corrosion, such as the formation of protective films, vary greatly with the conditions encountered.
The results obtained in the test should not, therefore, be regarded as a direct guide to the corrosion resistance of the tested materials in all environments
where these materials may be used. Also, performance of different materials in the test cannot always be taken as a direct guide to the relative corrosion
resistance of these materials in service.
6.5.3 On parts with Type II coatings, the greater number of hours for either white corrosion products or rust shall apply. For
example, for Type II, Class 5, the test shall be continued until the 72-h requi
...
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