ASTM B700-20

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: B700 − 08 (Reapproved 2014) B700 − 20
Standard Specification for
Electrodeposited Coatings of Silver for Engineering Use
This standard is issued under the fixed designation B700; 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
1.1 This specification covers requirements for electrodeposited coatings of silver used for engineering purposes that may be
mat,matt, 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 spectral
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 safety, health, and healthenvironmental practices and determine the applicability of regulatory limitations prior
to use.
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.
2. Referenced Documents
2.1 ASTM Standards:
B183 Practice for Preparation of Low-Carbon Steel for Electroplating
B242 Guide for Preparation of High-Carbon Steel for Electroplating
B252 Guide for Preparation of Zinc Alloy Die Castings for Electroplating and Conversion Coatings
B253 Guide for Preparation of Aluminum Alloys for Electroplating
B254 Practice for Preparation of and Electroplating on Stainless Steel
B281 Practice for Preparation of Copper and Copper-Base Alloys for Electroplating and Conversion Coatings
B322 Guide for Cleaning Metals Prior to Electroplating
B343 Practice for Preparation of Nickel for Electroplating with Nickel
B374 Terminology Relating to Electroplating
B481 Practice for Preparation of Titanium and Titanium Alloys for Electroplating
This specification is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.04 on
Precious Metal Coatings.
Current edition approved May 1, 2014Nov. 1, 2020. Published May 2014November 2020. Originally approved in 1981. Last previous edition approved in 20082014 as
B700 – 08.B700 – 08(2014). DOI: 10.1520/B0700-08R14.10.1520/B0700-20.
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
B700 − 20
B482 Practice for Preparation of Tungsten and Tungsten Alloys for 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
B504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
B507 Practice for Design of Articles to Be Electroplated on Racks
B542 Terminology Relating to Electrical Contacts and Their Use
B567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B571 Practice for Qualitative Adhesion Testing of Metallic Coatings
B578 Test Method for Microhardness of Electroplated Coatings
B579 Specification for Electrodeposited Coatings of Tin-Lead Alloy (Solder Plate)
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B678 Test Method for Solderability of Metallic-Coated Products
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
B849 Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
B850 Guide for Post-Coating Treatments of Steel for Reducing the Risk of Hydrogen Embrittlement
D3951 Practice for Commercial Packaging
E1004 Test Method for Determining Electrical Conductivity Using the Electromagnetic (Eddy Current) Method
F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
2.2 ANSI/ASQ Standard:
ANSI/ASQ Z1.4 Sampling Procedures And Tables For Inspection By Attributes
3. Terminology
3.1 Definitions—Many of the terms used in this specification are defined in Terminologies B374 or B542.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 rack-plating—rack-plating, n—an electrodeposition process in which articles to be coated are mounted on racks or other
fixtures during the process.
3.2.2 significant surfaces—surfaces, n—surfaces that are normally visible, directly or by reflection, or that are essential to the
serviceability or function of the article or which can be the source of corrosion products or tarnish films that interfere with the
function or desirable appearances of the article. When necessary, the significant surfaces shall be indicated on the drawings of the
parts, or by the provisions of suitably marked samples.
3.2.2.1 Discussion—
When necessary, the significant surfaces shall be indicated on the drawings of the parts, or by the provisions of suitably marked
samples.
3.2.2.2 Discussion—
Variation in the coating thickness from point-to-point on a coated article is an inherent characteristic of electroplating 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. The average coating thickness on the article usually will be greater
than that specified; how much greater is largely determined by the shape of the article (see Practice B507) and the characteristics
of the electroplating process. Additionally, the average coating thickness on an article will vary from article to article within a
production lot. If all the articles in a production lot are to meet the thickness requirement, the average coating thickness of a
production lot as a whole will be greater than the average necessary to ensure that a single article meets requirements.
3.2.3 strike or flash—flash, n—a thin, typically less than 0.25-μm0.25 μm (10 μ-in.) metallic coating layer between metallic
coatings to improve adhesion.
3.2.4 underplating—underplating, v—an application of a metallic coating layer between the basis metal or substrate and the
topmost metallic coating or coatings (see 6.3.4).
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
B700 − 20
4. Classification
4.1 Electrodeposited coatings of silver shall be classified for Type based on minimum purity,purity; Grade, whether bright,
semibright, or mat,matt; Class, if supplementary surface treatment is applied,applied; and thickness in micrometers.
4.2 Purity—Specify by Type as follows:
Type 1—99.9 % min
Type 2—99.0 % min
Type 3—98.0 % min
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 stated
function of the coating and are acceptable to the purchaser (see Appendix X1).
4.3 Surface Appearance—Specify by Grade in letter code as follows:
Grade A, MatMatt—Electrodeposits without luster, obtained from electroplating solutions operated without the use of
brighteners.
Grade B, Bright—Electrodeposits obtained by the use of brighteners in the electroplating bath.
Grade C, Bright—Electrodeposits obtained by mechanical or chemical polishing of Grade A silver coatings.
Grade D, Semibright— Semi-lustrous —Semi-lustrous electrodeposits obtained by the use of addition agents in the
electroplating bath.
4.4 Supplementary Surface Treatment—Specify by Class in letter code as follows:follows (see Appendix X5):
Class N—A silver finish that has had no supplementary tarnish resistant (that is, chromate) treatment (see treatment.Appendix
X5).
Class S—A silver finish that has had a supplementary tarnish resistant (that is, chromate) treatment.chromate treatment to resist
tarnishing.
NOTE 2—Class S is not suitable for food service applications.
Class T—A silver finish that has had a supplementary non-chromate treatment to resist tarnishing.
5. Ordering Information
5.1 To make application of this standard complete, the purchaser needs to supply the following information to the seller in the
purchase order or other governing document:
5.1.1 Name, designation, and year of issue of this standard.
5.1.2 Type (see 4.2), Grade (see 4.3), Class (see 4.4) and Thickness (see 6.6 and Appendix X3).
5.1.3 Nature of Substrate—If, for example, it is high strength steel, the need for stress relief (see 6.3.2.1) and embrittlement relief
(see 6.3.5.1). If it is copper, an undercoat is needed (see S1.3) for some applications.
5.1.4 Significant Surfaces (see section 3.2.2).
5.1.5 Appearance (see 6.7).
5.1.6 Underplates (see 6.3.4 and S1.3).
5.1.7 Requirements and methods of testing for one or more of the following: need for and type of test specimens (see 8.1),
thickness (see 6.6, 8.2, and Appendix X3), adhesion (see 6.8 and 8.3), hardness (see 6.10.1 and 8.7), absence of embrittlement (see
8.4), solderability (see 6.9 and 8.5), spectral reflectance (see 6.10.2 and 8.8), or electrical conductivity (see 6.10.3 and 8.9).
5.1.8 Sampling Plans and Quality Assurance (see Section 7 and S1.2).
B700 − 20
6. Coating Requirements
6.1 Nature of Coating—The coating essentially shall be silver, considering the type specified, produced by electrodeposition from
aqueous electrolytes.
6.2 Purity of Coating—The coating shall meet the chemical composition requirements of the specified type as defined in 4.2 and
measured as described in 8.6.
6.3 Process:
6.3.1 The basis metal shall be subjected to such cleaning procedures as are necessary to ensure a surface satisfactory for
subsequent electroplating. Materials used for cleaning shall have no damaging effects on the basis metal resulting in pits,
intergranular attack, stress corrosion cracking, or hydrogen embrittlement.
NOTE 2—For basis metal preparations, the following appropriate ASTM standards are recommended: Practices B183, B254, B281, B343, B481, and B482,
and Guides B242, B252, B253, and B322.
6.3.2 Preplating Operations—Electroplating shall be applied after all basis metal heat treatments and mechanical operations such
as forming, machining, and joining of the article have been completed.
NOTE 3—Silver deposits may be used to facilitate mechanical operations such as forming and drawing. In these applications, silver is applied before such
process steps.
6.3.2.1 Stress Relief Treatment—Parts that are made of steels with ultimate tensile strength of 1000 MPa or over (hardness of 31
HRC or greater) that have been machined, ground, cold-formedcold-formed, or cold-straightened subsequent to heat treatment,
may require stress relief heat treatment when specified by the purchaser, the tensile strength to be supplied by the purchaser.
Specification B849 may be consulted for a list of pretreatments that are used widely.
6.3.3 Strike—The final silver coating shall be preceded by a silver or gold strike for optimum adhesion.
6.3.4 Underplating—A nickel or nickel-alloy intermediate layer, at least 1 μm (39 μ-in.) thick, shall be applied before the silver
electroplate when the product being plated is made from copper or copper alloy. Nickel underplatings are also applied for other
reasons.
6.3.5 Post-Plating Procedures:
6.3.5.1 Embrittlement Relief—Parts that are made of steels with ultimate tensile strength of 100 MPa or over (hardness of 31 HRC
or greater), as well as surface-hardened parts, may require post-coating hydrogen embrittlement relief baking when specified by
the purchaser, the tensile strength to be supplied by the purchaser. SpecificationGuide B850 may be consulted for a list of
post-treatments that are used widely.
6.4 Surface Appearance—The coating’s surface finish shall meet the requirements of the specified grade defined in 4.3.
6.5 Supplementary Post Treatment—The coating shall meet the requirements of the specified class defined in 4.4.
6.6 Thickness—The silver coating thickness on significant surfaces shall be at least that specified (see Appendix X3) when
measured as described in 8.2.
6.7 Appearance—Silver electroplated coated articles shall be covered completely on all surfaces as specified in the manufacturing
document and shall have a uniform appearance with no visible defects to the extent that the nature of the basis metal and good
commercial practice permit. The requirement for uniform color or appearance need not apply for subsequent passivation or other
treatments of the silver.
6.7.1 Defects—Defects in the surface of the basis metal such as scratches, pits, non-conducting inclusions, and roll and die marks
B700 − 20
may adversely affect the appearance and performance of applied coatings. Such defects that persists in the finish despite the
observance of good metal finishing practices shall not be cause for rejection.
NOTE 4—Coated finishes generally perform better in service when the substrate over which they are applied is smooth and free from torn metal, inclusions,
pores, and other defects. It is recommended that the specifications covering the unfinished product providesprovide limits for those defects. A metal
finisher often can remove defects by means of special treatments such as grinding, polishing, abrasive blasting, chemical treatments, and electropolishing.
However, these are not normal for the treatment steps preceding application of the finish. When they are desired, they are the subject of special agreement
between the purchaser and the supplier.
6.8 Adhesion—The silver coatings shall be free of blisters and peeled areas indicating poor adhesion when tested in accordance
with 8.3.
NOTE 5—Some applications may require no separation by any mechanical means such as machining or milling through the interface.
6.9 Solderability—The silver plated surfaces shall produce solder coatings which shall be bright, smooth, and uniform. At least
95 % of the sample surface shall show good wetting when tested as described in 8.5.
6.10 Supplementary Requirements:
6.10.1 Hardness—If a hardness requirement is specified, the hardness of the silver coatings shall conform to that specified as
measured as described in 8.7.
6.10.2 Spectral Reflectance—The spectral reflectance of the silver coatings, if required, shall conform to that specified when
measured as described in 8.8.
6.10.3 Electrical Conductivity—
...