ASTM B488-95

Standard Specification for Electrodeposited Coatings of Gold for Engineering Uses

SCOPE
1.1 This specification covers requirements for electrodeposited gold coatings that contain not less than 99.00 mass % gold and that are used for engineering applications.
1.2 Specifically excluded from this specification are autocatalytic, immersion, and vapor deposited gold coatings.
1.3 Gold coatings conforming to this specification are employed for their corrosion and tarnish resistance (including resistance to fretting corrosion and catalytic polymerization), bondability, low and stable contact resistance, solderability, and infrared reflectivity. Several types of coatings, differing in gold purity and hardness, are covered by this specification.
1.4 The values stated in SI units are to be regarded as the standard. Values provided in parentheses are for information only.
1.5 The following hazards caveat pertains only to the test methods section, Section 9, 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.

General Information

• Status: Historical
• Publication Date: 09-Oct-2001
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.04 - Precious Metal Coatings

Relations

• Replaced By: ASTM B488-01 - Standard Specification for Electrodeposited Coatings of Gold for Engineering Uses
• Effective Date: 10-Oct-2001
• Referred By: ASTM B877-96(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by the Phosphomolybdic Acid (PMA) Method
• Effective Date: 10-Oct-2001
• Referred By: ASTM B866-95(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by Polysulfide Immersion
• Effective Date: 10-Oct-2001
• Referred By: ASTM B679-98(2021) - Standard Specification for Electrodeposited Coatings of Palladium for Engineering Use
• Effective Date: 10-Oct-2001
• Referred By: ASTM B984-12(2020)e1 - Standard Specification for Electrodeposited Coatings of Palladium-Cobalt Alloy for Engineering Use
• Effective Date: 10-Oct-2001
• Referred By: ASTM B867-95(2018) - Standard Specification for Electrodeposited Coatings of Palladium-Nickel for Engineering Use
• Effective Date: 10-Oct-2001

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 488 – 95
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Specification for
Electrodeposited Coatings of Gold for Engineering Uses
This standard is issued under the fixed designation B 488; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope B 322 Practice for Cleaning Metals Prior to Electroplating
B 343 Practice for Preparation of Nickel for Electroplating
1.1 Purity—This specification covers requirements for elec-
with Nickel
trodeposited gold coatings that contain not less than 99.00
B 374 Terminology Relating to Electroplating
mass % gold and that are used for engineering applications.
B 481 Practice for Preparation of Titanium and Titanium
1.2 Specifically excluded from this specification are auto-
Alloys for Electroplating
catalytic, immersion, and vapor deposited gold coatings.
B 482 Practice for Preparation of Tungsten and Tungsten
1.3 Properties—Gold coatings conforming to this specifi-
Alloys for Electroplating
cation are employed for their corrosion and tarnish resistance
B 487 Test Method for Measurement of Metal and Oxide
(including resistance to fretting corrosion and catalytic poly-
Coating Thicknesses by Microscopical Examination of a
merization), bondability, low and stable contact resistance,
Cross Section
solderability, and infrared reflectivity. Several types of coat-
B 489 Practice for Bend Test for Ductility of Electrodepos-
ings, differing in gold purity and hardness, are covered by this
ited and Autocatalytically Deposited Metal Coatings on
specification.
Metals
1.4 The values stated in SI units are to be regarded as the
B 499 Test Method for Measurement of Coating Thick-
standard. Values provided in parentheses are for information
nesses by the Magnetic Method: Nonmagnetic Coatings on
only.
Magnetic Basis Metals
1.5 The following hazards caveat pertains only to the test
B 504 Test Method for Measurement of Thickness of Me-
methods section, Section 9, of this specification: This standard
tallic Coatings by the Coulometric Method
does not purport to address all of the safety concerns, if any,
B 507 Practice for Design of Articles to Be Electroplated on
associated with its use. It is the responsibility of the user of this
Racks
standard to establish appropriate safety and health practices
B 542 Terminology Relating to Electrical Contacts and
and determine the applicability of regulatory limitations prior
Their Use
to use.
B 558 Practice for Preparation of Nickel Alloys for Electro-
2. Referenced Documents
plating
B 567 Test Method for Measurement of Coating Thickness
2.1 ASTM Standards:
by the Beta Backscatter Method
B 32 Specification for Solder Metal
B 568 Test Method for Measurement of Coating Thickness
B 183 Practice for Preparation of Low-Carbon Steel for
by X-Ray Spectrometry
Electroplating
B 571 Test Methods for Adhesion of Metallic Coatings
B 242 Practice for Preparation of High-Carbon Steel for
B 578 Test Method for Microhardness of Electroplated
Electroplating
Coatings
B 253 Guide for Preparation of Aluminum Alloys for Elec-
B 602 Test Method for Attribute Sampling of Metallic and
troplating
Inorganic Coatings
B 254 Practice for Preparation of and Electroplating on
B 697 Guide for Selection of Sampling Plans for Inspection
Stainless Steel
of Electrodeposited Metallic and Inorganic Coatings
B 281 Practice for Preparation of Copper and Copper Base
B 735 Test Method for Porosity in Gold Coatings on Metal
Alloys for Electroplating and Conversion Coatings
Substrates by Nitric Acid Vapor
B 741 Test Methods for Porosity in Gold Coatings on Metal
1 3
This specification is under the jurisdiction of ASTM Committee B-8 on
Substrates by Paper Electrography
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee
B 748 Test Method for Measurement of Thickness of Me-
B08.08on Engineering Coatings.
tallic Coatings by Measurement of Cross Section with a
Current edition approved Jan. 15, 1995. Published April 1995. Originally
published as B 488 – 68. Last previous edition B 488 – 86e .
Annual Book of ASTM Standards, Vol 02.04.
3 4
Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 03.04.
B 488
Scanning Electron Microscope (SEM) 4.2.2 Hardness—Hardness values shall be indicated by
B 762 Method of Variables Sampling of Metallic and Inor- ASTM code. The military standard designation of grade is
ganic Coatings included for reference.
B 765 Guide for Selection of Porosity Tests for Electrode-
Knoop Hardness Range ASTM Code MIL-G-45204
90 HK maximum A A
posits and Related Metallic Coatings 25
91–129 HK . B
B 799 Test Method for Porosity in Gold and Palladium
90–200 HK B (see Note 1) .
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
130–200 HK CC
>200 HK DD
B 809 Test Method for Porosity in Metallic Coatings by
Humid Sulfur Vapor (Flowers-of-Sulfur)
NOTE 1—This designation is retained, although rarely used, because
some specifications reference it.
D 509 Test Methods of Sampling and Grading Rosin
D 1125 Test Methods for Electrical Conductivity and Re-
4.2.3 Relationship Between Purity and Hardness—The fol-
sistivity of Water
lowing combinations of purity and hardness ranges are repre-
D 3951 Practice for Commercial Packaging
sentative of good commercial practice:
F 390 Test Method for Sheet Resistance of Thin Metallic
Type Code
Films with a Collinear Four-Probe Array
1 A only
2 A, B, and C
2.2 U.S. Government Standards:
3 C and D
MIL STD 105 Sampling Procedures and Tables for Inspec-
4.3 Thickness—Thickness shall be specified by an arabic
tion by Attributes
MIL-G-45204 Gold Plating, Electrodeposited numeral that designates the minimum linear thickness in
micrometres. Examples of commonly specified thicknesses are
3. Terminology
shown in Table 1. Unless otherwise specified, the density of
3 3
gold is assumed to be 19.3 g/cm for Type 1 and 17.5 g/cm for
3.1 Definitions—For definitions of terms used in this speci-
Type 2 and Type 3.
fication refer to Terminologies B 374 or B 542.
4.3.1 See 7.4.2 for thickness tolerances.
3.2 Definitions of Terms Specific to This Standard:
4.3.2 Instead of specifying the thickness in micrometres, the
3.2.1 significant surfaces—defined as those normally vis-
purchaser may specify the mass of gold per unit area (coating
ible (directly or by reflection) or essential to the serviceability
weight) in milligrams per square centimeter. Unless otherwise
or function of the article. Can be the source of corrosion
specified, the density of gold is assumed to be 19.3 g/cm for
products or tarnish films that interfere with the function or
Type 1 and 17.5 g/cm for Type 2 and Type 3.
desirable appearance of the article. The significant surfaces
shall be indicated on the drawings of the parts or by the
NOTE 2—When significant surfaces are involved on which the specified
provision of suitably marked samples.
thickness of deposit cannot readily be controlled, such as threads, holes,
3.2.2 underplating—a metallic coating layer between the
deep recesses, bases of angles, and similar areas, the purchaser and the
manufacturer should recognize the necessity for either thicker deposits on
basis metal or substrate and the topmost metallic coating. The
the more accessible surfaces or for special racking. Special racks may
thickness of an underplating is usually greater than 1 μm (40
involve the use of conforming, auxiliary, bipolar electrodes, or noncon-
μin.), in contrast to a strike or flash, which is thinner.
ducting shields.
4. Classification
5. Ordering Information
4.1 Types of Coatings—A coating shall be specified by a
5.1 To make the application of this standard complete, the
combination of the following:
purchaser needs to supply the following information to the
4.1.1 type, characterizing minimum purity in accordance
seller in the purchase order or other governing document.
with 4.2.1,
5.1.1 The name, designation, and date of issue of this
4.1.2 code, designating Knoop hardness in accordance with
specification.
4.2.2, and
5.1.2 Classification: type, code, and thickness (or mass per
4.1.3 a numeral designating thickness in micrometres in
unit area) (see Section 4).
accordance with 4.3.
5.1.3 Presence and thickness of underplating, if required
4.2 Purity and Hardness:
(see 3.2.1).
4.2.1 Purity—Purity shall be specified by ASTM type. The
5.1.4 Significant surfaces shall be specified (see 3.2.2).
military standard designation of type is included for reference.
5.1.5 Requirement, if any, for performance testing such as
Mass Percent Gold, Minimum ASTM Type MIL-G-45204
porosity testing (see 9.6), solderability testing (see Appendix
99.90 1 III
X4), ductility testing (see 9.7), etc.
99.70 2 I
99.00 3 II
TABLE 1 Coating Thickness
Class Minimum Thickness, μm
0.25 0.25
0.50 0.50
Annual Book of ASTM Standards, Vol 06.03.
0.75 0.75
Annual Book of ASTM Standards, Vol 11.01.
1.0 1.0
Annual Book of ASTM Standards, Vol 15.09.
8 1.25 1.25
Annual Book of ASTM Standards, Vol 10.04.
9 2.5 2.5
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
5.0 5.0
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
B 488
are employed, such as in wave guides, the magnetic properties of nickel
5.1.6 If the substrate is one that requires a nickel underplat-
may attenuate the signal.
ing (see 6.6.1 and Appendix X6).
NOTE 6—In applications in which forming or flaring operations are to
5.1.7 Whether or not stress relief has been or is to be done
be applied to the plated component, a ductile nickel electrodeposit should
(steel parts only).
be specified.
5.1.8 Sampling plan employed (see Section 8).
6.5.2 Strikes—It is recommended to apply a gold strike to
the underplate or substrate, except if the latter is silver or
6. Manufacture
platinum, prior to applying the gold top coating.
6.1 Any process that provides an electrodeposit capable of
6.5.3 Plating—Good practice calls for parts to be electri-
meeting the specified requirements is acceptable.
cally connected when entering the gold plating solution. A
6.2 Substrate:
minimum of 0.5 V is suggested.
6.2.1 The surface condition of the basis metal should be
NOTE 7—For rack and barrel plating processing, residual plating salts
specified and should meet this specification prior to the plating
can be removed from the articles by a clean, hot (50 to 100°C) water rinse.
of the parts.
A minimum rinse time of 2.5 min (rack) or 5 min (barrel) is suggested.
6.2.2 Defects in the surface of the basis metal such as
Best practice calls for a minimum of three dragout rinses and one running
scratches, porosity, pits, inclusions, roll and die marks, laps,
rinse with dwell times of 40 s in each station when rack plating and 80 s
cracks, burrs, cold shuts, and roughness may adversely affect
when barrel plating. Modern, high-velocity impingement-type rinses can
the appearance and performance of the deposit, despite the reduce this time to a few seconds. This is particularly useful in automatic
reel-to-reel applications in which dwell times are significantly reduced.
observance of the best plating practice. Any such defects on
significant surfaces shall be brought to the attention of the
7. Coating Requirements
purchaser.
7.1 Nature of Coating—The gold deposit shall meet the
6.2.3 The basis metal shall be subject to such cleaning
appropriate purity requirements as put forth in the following:
procedures as are necessary to ensure a satisfactory surface for
7.1.1 Type 1 (Type III according to MIL-G-45204) coatings
subsequent electroplating (see Practices B 183, B 242, Guide
shall contain at least 99.90 mass % gold. Individual metallic
B 253, Practices B 254, B 281, B 322, B 343, B 481, B 482,
impurities shall not be present in a quantity greater than 0.04
and B 558).
mass %. Iron, nickel, and cobalt combined shall be less than
6.2.4 Proper preparatory procedures and thorough cleaning
0.05 mass %, and none of these three elements shall be present
of the basis metal are essential for satisfactory adhesion and
in an amount greater than 0.03 mass %. The gold content shall
performance of these coatings. The surface must be chemically
be calculated by difference.
clean and continuously conductive, that is, without inclusions
7.1.2 Type 2 (Type 1 according to MIL-G-45204) coatings
or other contaminants. They must be smooth and as free of
shall contain at least 99.70 mass % gold. For Type 2 Code A
scratches, gouges, nicks, and similar imperfections as possible.
coatings only, metallic hardening agents such as nickel, cobalt,
NOTE 3—A metal finisher can often remove defects through special
and iron combined shall be less than 0.05 mass % and, none of
treatments such as grinding, polishing, abrasive blasting, chemical treat-
these three elements shall be present in an amount greater than
ments, and electropolishing. However, these may not be normal in the
0.03 mass %. The gold content shall be calculated by differ-
treatment steps preceding the plating and a special agreement is indicated.
ence.
6.3 If required (see 5.1.7), steel parts with a hardness greater
7.1.3 Type 3 (Type II according to MIL-G-45204) coatings
than 31 HRC shall be given a suitable stress relief heat
shall contain at least 99.00 mass % gold and may contain
treatment prior to plating. Such stress relief shall not reduce the
metallic hardening agents, which may be present in amounts
hardness to a value below the specified minimum. Acid
greater than 0.1 mass %. All other metals shall be considered
pickling of high strength steels shall be avoided.
impurities and shall not be present in amounts greater than 0.1
6.3.1 The coating shall be applied after all basis metal heat
mass % each. The gold content shall be calculated by differ-
treatments and mechanical operations on significant surfaces
ence.
have been completed.
7.2 Hardness—The gold coating shall have a Knoop hard-
6.4 Racking—Parts should be positioned so as to allow free
ness within the specified range as shown in 4.2.2 when tested
circulation of solution over all surfaces. The location of rack or
in accordance with 9.2.
wire marks in the coating shall be agreed upon between the
7.3 Appearance—Gold coatings shall be coherent, continu-
producer and the supplier.
ous, and have a uniform appearance to the extent tha
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