ASTM B700-97
(Test Method)Standard Test Method for Electrodeposited Coatings of Silver for Engineering Use
Standard Test Method for Electrodeposited Coatings of Silver for Engineering Use
SCOPE
1.1 This specification covers requirements for electrodeposited coatings of silver used for engineering purposes that may be mat, bright, or semibright and are not less than 98% silver purity.
1.2 Coatings of silver covered by this specification are usually employed for solderable surfaces, electrical contact characteristics, high electrical and thermal conductivity, thermocompression bonding, wear resistance of load-bearing surfaces, and special reflectivity.
1.3 In the Appendixes important characteristics of electrodeposited silver coatings are briefly described which must be considered when used in engineering applications, namely electrical conductivity (see Appendix X1), silver migration (see Appendix X2), thickness (see Appendix X3), hardness (see Appendix X4), and atmospheric tarnish (see Appendix X5).
1.4 The following hazards caveat pertains only to the test methods section of this specification: 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.
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Designation: B 700 – 97
Standard Specification for
Electrodeposited Coatings of Silver for Engineering Use
This standard is issued under the fixed designation B 700; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope B 343 Practice for Preparation of Nickel for Electroplating
with Nickel
1.1 This specification covers requirements for electrodepos-
B 374 Terminology Relating to Electroplating
ited coatings of silver used for engineering purposes that may
B 481 Practice for Preparation of Titanium and Titanium
be mat, bright, or semibright and are not less than 98 % silver
Alloys for Electroplating
purity.
B 482 Practice for Preparation of Tungsten and Tungsten
1.2 Coatings of silver covered by this specification are
Alloys for Electroplating
usually employed for solderable surfaces, electrical contact
B 487 Test Method for Measurement of Metal and Oxide
characteristics, high electrical and thermal conductivity, ther-
Coating Thicknesses by Microscopical Examination of a
mocompression bonding, wear resistance of load-bearing sur-
Cross Section
faces, and spectral reflectivity.
B 499 Test Method for Measurement of Coating Thick-
1.3 In the Appendixes important characteristics of elec-
nesses by the Magnetic Method: Nonmagnetic Coatings on
trodeposited silver coatings are briefly described which must
Magnetic Basis Metals
be considered when used in engineering applications, namely
B 504 Test Method for Measurement of Thickness of Me-
electrical conductivity (see Appendix X1), silver migration
tallic Coatings by the Coulometric Method
(see Appendix X2), thickness (see Appendix X3), hardness (see
B 507 Practice for Design of Articles to be Electroplated on
Appendix X4), and atmospheric tarnish (see Appendix X5).
Racks
1.4 The following hazards caveat pertains only to the test
B 542 Terminology Relating to Electrical Contacts and
methods section of this specification: This standard does not
Their Use
purport to address the safety concerns, if any, associated with
B 567 Test Method for Measurement of Coating Thickness
its use. It is the responsibility of the user of this standard to
by the Beta Backscatter Method
establish appropriate safety and health practices and deter-
B 568 Test Method for Measurement of Coating Thickness
mine the applicability of regulatory limitations prior to use.
by X-Ray Spectrometry
2. Referenced Documents
B 571 Test Methods for Adhesion of Metallic Coatings
B 578 Test Method for Microhardness of Electroplated
2.1 ASTM Standards:
Coatings
B 183 Practice for Preparation of Low-Carbon Steel for
B 579 Specification for Electrodeposited Coatings of Tin-
Electroplating
Lead Alloy (Solder Plate)
B 242 Practice for Preparation of High-Carbon Steel for
B 602 Test Method for Attribute Sampling of Metallic and
Electroplating
Inorganic Coatings
B 252 Guide for Preparation of Zinc Alloy Die Castings for
B 678 Test Method for Solderability of Metallic-Coated
Electroplating Conversion Coatings
Products
B 253 Guide for Preparation of Aluminum Alloys for Elec-
B 697 Guide for Selection of Sampling Plans for Inspection
troplating
of Electrodeposited Metallic and Inorganic Coatings
B 254 Practice for Preparation of and Electroplating on
B 762 Method of Variables Sampling of Metallic and Inor-
Stainless Steel
ganic Coatings
B 281 Practice for Preparation of Copper and Copper-Base
B 849 Specification for Pre-treatments of Iron or Steel for
Alloys for Electroplating and Conversion Coatings
Reducing the Risk of Hydrogen Embrittlement
B 322 Practice for Cleaning Metals Prior to Electroplating
B 850 Specification for Post-Coating Treatments of Iron or
Steel for Reducing the Risk of Hydrogen Embrittlement
D 3951 Practice for Commercial Packaging
This specification is under the jurisdiction of ASTM Committee B-8 on E 1004 Test Method for Electromagnetic (Eddy-Current)
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.08.01 on Engineering Coatings.
Current edition approved May 10, 1997. Published February 1998. Originally Annual Book of ASTM Standards, Vol 03.04.
published as B 700 – 81. Last previous edition B 700 – 90. Annual Book of ASTM Standards, Vol 15.09.
Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
B 700
Measurements of Electrical Conductivity 4.3 Surface Appearance—Specify by Grade in letter code
F 519 Method for Mechanical Hydrogen Embrittlement as follows:
Testing of Plating Processes and Aircraft Maintenance Grade A, Mat—Electrodeposits without luster, obtained
Chemicals from electroplating solutions operated without the use of
brighteners.
3. Terminology
Grade B, Bright—Electrodeposits obtained by the use of
3.1 Definitions—Many of the terms used in this specifica- brighteners in the electroplating bath.
Grade C, Bright—Electrodeposits obtained by mechanical
tion are defined in Terminologies B 374 or B 542.
3.2 Definitions of Terms Specific to This Standard: or chemical polishing of Grade A silver coatings.
Grade D, Semibright—Electrodeposits obtained by the use
3.2.1 rack-plating—an electrodeposition process in which
articles to be coated are mounted on racks or other fixtures of addition agents in the electroplating bath.
4.4 Supplementary Surface Treatment— Specify by Class in
during the process.
3.2.2 significant surfaces—surfaces that are normally vis- letter code as follows:
Class N—A finish that has had no supplementary tarnish
ible, directly or by reflection, or that are essential to the
serviceability or function of the article or which can be the resistant (that is, chromate) treatment (see Appendix X5).
source of corrosion products or tarnish films that interfere with Class S—A finish that has had a supplementary tarnish
the function or desirable appearances of the article. When resistant (that is, chromate) treatment.
necessary, the significant surfaces shall be indicated on the
NOTE 2—Class S is not suitable for food service applications.
drawings of the parts, or by the provisions of suitably marked
samples.
5. Ordering Information
3.2.2.1 Discussion—Variation in the coating thickness from
5.1 To make application of this standard complete, the
point-to-point on a coated article is an inherent characteristic of
purchaser needs to supply the following information to the
electroplating processes. Therefore, the coating thickness will
seller in the purchase order or other governing document:
have to exceed the specified value at some points on the
5.1.1 Name, designation, and year of issue of this standard.
significant surfaces to ensure that the thickness equals or
5.1.2 Type (see 4.2), Grade (see 4.3), Class (see 4.4) and
exceeds the specified value at all points. The average coating
Thickness (see 6.6 and Appendix X3).
thickness on the article usually will be greater than that
5.1.3 Nature of Substrate—If, for example, it is high
specified; how much greater is largely determined by the shape
strength steel, the need for stress relief (see 6.3.2.1) and
of the article (see Practice B 507) and the characteristics of the
embrittlement relief (see 6.3.5.1). If it is copper, an undercoat
electroplating process. Additionally, the average coating thick-
is needed (see S1.3) for some applications.
ness on an article will vary from article to article within a
5.1.4 Significant Surfaces (see section 3.2.2).
production lot. If all the articles in a production lot are to meet
5.1.5 Appearance (see 6.7).
the thickness requirement, the average coating thickness of a
5.1.6 Underplates (see 6.3.4 and S1.3).
production lot as a whole will be greater than the average
5.1.7 Requirements and methods of testing for one or more
necessary to ensure that a single article meets requirements.
of the following: need for and type of test specimens (see 8.1),
3.2.3 strike or flash—a thin, typically less than 0.25-μm (10
thickness (see 6.6, 8.2, and Appendix X3), adhesion (see 6.8
μ-in.) metallic coating layer between metallic coatings to
and 8.3), hardness (see 6.10.1 and 8.7), absence of embrittle-
improve adhesion.
ment (see 8.4), solderability (see 6.9 and 8.5), spectral reflec-
3.2.4 underplating—an application of a metallic coating
tance (see 6.10.2 and 8.8), or electrical conductivity (see 6.10.3
layer between the basis metal or substrate and the topmost
and 8.9).
metallic coating or coatings (see 6.3.4).
5.1.8 Sampling Plans and Quality Assurance (see Section 7
and S1.2).
4. Classification
4.1 Electrodeposited coatings of silver shall be classified for
6. Coating Requirements
Type based on minimum purity, Grade whether bright,
6.1 Nature of Coating—The coating essentially shall be
semibright, or mat, Class if supplementary surface treatment is
silver, considering the type specified, produced by electrodepo-
applied, and thickness in micrometers.
sition from aqueous electrolytes.
4.2 Purity—Specify by Type as follows:
6.2 Purity of Coating—The coating shall meet the chemical
Type 1—99.9 % min
composition requirements of the specified type as defined in
Type 2—99.0 % min
4.2 and measured as described in 8.6.
Type 3—98.0 % min
6.3 Process:
6.3.1 The basis metal shall be subjected to such cleaning
NOTE 1—Metallic or organic brighteners used for grain refinement may
be present in the electrodeposit so long as they do not interfere with the procedures as are necessary to ensure a surface satisfactory for
stated function of the coating and are acceptable to the purchaser (see
subsequent electroplating. Materials used for cleaning shall
Appendix X1).
have no damaging effects on the basis metal resulting in pits,
intergranular attack, stress corrosion cracking, or hydrogen
embrittlement.
Annual Book of ASTM Standards, Vol 03.03.
Annual Book of ASTM Standards, Vol 15.03. NOTE 3—For basis metal preparations, the following appropriate
B 700
ASTM standards are recommended: Practices B 183, B 242, B 252, electropolishing. However, these are not normal for the treatment steps
B 254, B 281, B 322, B 343, B 481, and B 482, and Guide B 253. preceding application of the finish. When they are desired, they are the
subject of special agreement between the purchaser and the supplier.
6.3.2 Preplating Operations—Electroplating shall be ap-
6.8 Adhesion—The silver coatings shall be free of blisters
plied after all basis metal heat treatments and mechanical
and peeled areas indicating poor adhesion when tested in
operations such as forming, machining, and joining of the
accordance with 8.3.
article have been completed.
NOTE 6—Some applications may require no separation by any me-
NOTE 4—Silver deposits may be used to facilitate mechanical opera-
chanical means such as machining or milling through the interface.
tions such as forming and drawing. In these applications, silver is applied
before such process steps.
6.9 Solderability—The silver plated surfaces shall produce
solder coatings which shall be bright, smooth, and uniform. At
6.3.2.1 Stress Relief Treatment—Parts that are made of
least 95 % of the sample surface shall show good wetting when
steels with ultimate tensile strength of 1000 MPa or over
tested as described in 8.5.
(hardness of 31 HRC or greater) that have been machined,
6.10 Supplementary Requirements:
ground, cold-formed or cold-straightened subsequent to heat
6.10.1 Hardness—If a hardness requirement is specified, the
treatment, may require stress relief heat treatment when speci-
hardness of the silver coatings shall conform to that specified
fied by the purchaser, the tensile strength to be supplied by the
as measured as described in 8.7.
purchaser. Specification B 849 may be consulted for a list of
6.10.2 Spectral Reflectance—The spectral reflectance of the
pretreatments that are used widely.
silver coatings, if required, shall conform to that specified
6.3.3 Strike—The final silver coating shall be preceded by a
when measured as described in 8.8.
silver or gold strike for optimum adhesion.
6.10.3 Electrical Conductivity—The electrical conductivity
6.3.4 Underplating—A nickel or nickel-alloy intermediate
of the silver coatings, if required, shall conform to that
layer, at least 1 μm thick, shall be applied before the silver
specified when measured as described in 8.9.
electroplate when the product being plated is made from
copper or copper alloy. Nickel underplatings are also applied
7. Sampling
for other reasons.
7.1 A random sample of the size required by Test Method
6.3.5 Post-Plating Procedures:
B 602 or Method B 762 shall be selected from the inspection
6.3.5.1 Embrittlement Relief—Parts that are made of steels
lot (see 7.2). The articles in the lot shall be classified as
with ultimate tensile strength of 100 MPa or over (hardness of
conforming or nonconforming to each requirement according
31 HRC or greater), as well as surface-hardened parts, may
to the criteria of the sampling plans in the chosen method.
require post-coating hydrogen embrittlement relief baking
NOTE 7—Test Method B 602 contains four sampling plans, three for
when specified by the purchaser, the tensile strength to be
use with nondestructive test methods; the fourth is for use with destructive
supplied by the purchaser. Specification B 850 may be con-
test methods. The three methods for nondestructive tests differ in the
sulted for a list of post-treatments that are used widely.
quality level they require of the product. Test Method B 602 requires use
6.4 Surface Appearance—The coating’s surface finish shall
of the plan with the intermediate quality level unless the purchaser
meet the requirements of the specified grade defined in 4.3.
specifies otherwise. It is recommended that the purchaser compare the
6.5 Supplementary Post Treatment—The coating shall meet
plans with his needs and state which plan is to be used. If the plans in Test
Method B 602 do not serve the needs, additional ones are given in Guide
the requirements of the specified class defined in 4.4.
B 697 which provides a large number of plans and also gives guidance in
6.6 Thickness—The silver coating thickness on significant
the choice of a plan. When Guide B 697 is specified, the buyer and seller
surfaces shall be at least that specified (see Appendix X3) when
need to agree on the plan to be used.
measured as described in 8.2.
NOTE 8—Method B 762 is a variables sampling plan. Such plans can
6.7 Appearance—Silver electroplated coated articles shall
only be used when a test yields a measured quantity, such as
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