ASTM B766-86(2003)
(Specification)Standard Specification for Electrodeposited Coatings of Cadmium
Standard Specification for Electrodeposited Coatings of Cadmium
SCOPE
1.1 This specification covers the requirements for electrodeposited cadmium coatings on products of iron, steel, and other metals.
Note 1—Cadmium is deposited as a coating principally on iron and steel products. It can also be electrodeposited on aluminum, brass, beryllium copper, copper, nickel, and powder metallurgy parts.
1.2 The coating is provided in various thicknesses up to and including 25 μm either as electrodeposited or with supplementary finishes.
1.3 Cadmium coatings are used for corrosion resistance and for corrosion prevention of the basis metal part. The as-deposited coating (Type I) is useful for the lowest cost protection in a mild or noncorrosive environment where early formation of white corrosion products is not detrimental or harmful to the function of a component. The prime purpose of the supplementary chromate finishes (Types II and III) on the electroplated cadmium is to increase corrosion resistance. Chromating will retard or prevent the formation of white corrosion products on surfaces exposed to various environmental conditions as well as delay the appearance of corrosion from the basis metal.
1.4 Cadmium plating is used to minimize bi-metallic corrosion between high-strength steel fasteners and aluminum in the aerospace industry. Undercutting of threads on fastener parts is not necessary as the cadmium coating has a low coefficient of friction that reduces the tightening torque required and allows repetitive dismantling.
1.5 Cadmium-coated parts can easily be soldered without the use of corrosive fluxes. Cadmium-coated steel parts have a lower electrical contact resistance than zinc-coated steel. The lubricity of cadmium plating is used on springs for doors and latches and for weaving machinery operating in high humidity. Corrosion products formed on cadmium are tightly adherent. Unlike zinc, cadmium does not build up voluminous corrosion products on the surface. This allows for proper functioning during corrosive exposure of moving parts, threaded assemblies, valves, and delicate mechanisms without jamming with debris.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: B 766 – 86 (Reapproved 2003)
Standard Specification for
Electrodeposited Coatings of Cadmium
This standard is issued under the fixed designation B 766; 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 products on the surface. This allows for proper functioning
during corrosive exposure of moving parts, threaded assem-
1.1 This specification covers the requirements for electrode-
blies, valves, and delicate mechanisms without jamming with
posited cadmium coatings on products of iron, steel, and other
debris.
metals.
NOTE 1—Cadmium is deposited as a coating principally on iron and 2. Referenced Documents
steel products. It can also be electrodeposited on aluminum, brass,
2.1 The following standards form a part of this document to
beryllium copper, copper, nickel, and powder metallurgy parts.
the extent referenced herein.
1.2 The coating is provided in various thicknesses up to and
2.2 ASTM Standards:
including 25 µm either as electrodeposited or with supplemen-
A 165 Specification for Electrodeposited Coatings of Cad-
tary finishes.
mium on Steel
1.3 Cadmium coatings are used for corrosion resistance and
B 117 Practice for Operating Salt Spray (Fog) Apparatus
for corrosion prevention of the basis metal part. The as-
B 183 Practice for Preparation of Low-Carbon Steel for
deposited coating (Type I) is useful for the lowest cost
Electroplating
protection in a mild or noncorrosive environment where early
B 201 Practice for Testing Chromate Coatings on Zinc and
formation of white corrosion products is not detrimental or
Cadmium Surfaces
harmful to the function of a component. The prime purpose of
B 242 Practice for Preparation of High-Carbon Steel for
the supplementary chromate finishes (Types II and III) on the
Electroplating
electroplated cadmium is to increase corrosion resistance.
B 253 Guide for Preparation ofAluminumAlloys for Elec-
Chromating will retard or prevent the formation of white
troplating
corrosionproductsonsurfacesexposedtovariousenvironmen-
B 254 Practice for Preparation of and Electroplating on
talconditionsaswellasdelaytheappearanceofcorrosionfrom
Stainless Steel
the basis metal.
B 281 Practice for Preparation of Copper and Copper-Base
1.4 Cadmium plating is used to minimize bi-metallic corro-
Alloys for Electroplating and Conversion Coatings
sion between high-strength steel fasteners and aluminum in the
B 320 Practice for Preparation of Iron Castings for Electro-
aerospace industry. Undercutting of threads on fastener parts is
plating
not necessary as the cadmium coating has a low coefficient of
B 322 Practice for Cleaning Metals Prior to Electroplating
friction that reduces the tightening torque required and allows
B 343 Practice for Preparation of Nickel for Electroplating
repetitive dismantling.
with Nickel
1.5 Cadmium-coated parts can easily be soldered without
B 374 Terminology Relating to Electroplating
the use of corrosive fluxes. Cadmium-coated steel parts have a
B 487 Test Method for Measurement of Metal and Oxide
lower electrical contact resistance than zinc-coated steel. The
Coating Thicknesses by Microscopical Examination of a
lubricity of cadmium plating is used on springs for doors and
Cross Section
latches and for weaving machinery operating in high humidity.
B 499 Test Method for Measurement of Coating Thick-
Corrosion products formed on cadmium are tightly adherent.
nessesbytheMagneticMethod:NonmagneticCoatingson
Unlike zinc, cadmium does not build up voluminous corrosion
Magnetic Basis Metals
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee Discontinued; see 1987 Annual Book of ASTM Standards, Vol 02.05. Replaced
B08.08.04on Soft Metals. by Specification B 766.
Current edition approved Feb. 10, 2003. Published May 2003. Originally Annual Book of ASTM Standards, Vol 03.02.
approved in 1986. Last previous edition approved in 1998 as B 766 – 86 (1998). Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 766 – 86 (2003)
NOTE 3—It is strongly recommended that production items be pro-
B 504 Test Method for Measurement of Thickness of Me-
cessed as either Type II or Type III.
tallic Coatings by the Coulometric Method
B 507 PracticeforDesignofArticlestoBeElectroplatedon
5. Ordering Information
Racks
5.1 In order to make the application of this specification
B 558 Practice for Preparation of NickelAlloys for Electro-
complete, the purchaser needs to supply the following infor-
plating
mation to the seller in the purchase order or other governing
B 567 Test Method for Measurement of Coating Thickness
document:
by the Beta Backscatter Method
5.1.1 The name, designation, and date of issue of this
B 568 Test Method for Measurement of Coating Thickness
specification.
by X-Ray Spectrometry
5.1.2 Deposit by class and type (4.1 and 4.2).
B 571 Practice for QualitativeAdhesion Testing of Metallic
5.1.3 Composition and metallurgical condition of the sub-
Coatings
strate to be coated. Application to high-strength steel parts
B 602 Test Method for Attribute Sampling of Metallic and
(6.2).
Inorganic Coatings
5.1.4 Heat treatment for stress relief, whether it has been
B 697 Guide for Selection of Sampling Plans for Inspection
performed or is required (6.3).
of Electrodeposited Metallic and Inorganic Coatings
5 5.1.5 Additional undercoat, if required (6.5).
E 8 TestMethodsforTensionTestingofMetallicMaterials
5.1.6 Plating process variation, if required (6.6).
F 519 Method for Mechanical Hydrogen Embrittlement
6 5.1.7 Hydrogen embrittlement relief, if required (6.7).
EvaluationofPlatingProcessesandServiceEnvironments
5.1.8 Desired color of the Type II film (6.8.2).
2.3 Federal Standard:
7 5.1.9 Location of significant surfaces (7.1.2).
QQ-P-416 Plating, Cadmium (Electrodeposited)
5.1.10 Coating luster (7.5).
2.4 International Standard:
5.1.11 Whethernon-destructiveordestructivetestsaretobe
ISO 2082 Metallic Coatings—Electroplated Coatings of
used in cases of choice (Note 14).
Cadmium on Iron or Steel
5.1.12 Configuration, procedures, and tensile load for hy-
2.5 Military Standard:
9 drogen embrittlement relief test (9.4, 10.6, Supplementary
MIL-STD-1312 Fasteners, Test Methods
Requirements S2, and S3).
5.1.13 Whether certification is required (Section 12).
3. Terminology
5.1.14 Whether supplementary requirements are applicable.
3.1 Definitions—Definitions of terms used in this specifica-
tion are in accordance with Terminology B 374. 6. Materials and Manufacture
6.1 Nature of Coating—The coating shall be essentially
4. Classification
pure cadmium produced by electrodeposition usually from an
4.1 Classes—Electrodeposited cadmium coatings shall be alkaline cyanide solution.
classified on the basis of thickness as follows: 6.2 High Tensile Strength Steel Parts— Steel parts having
an ultimate tensile strength greater than 1650 MPa (approxi-
Class Minimum Thickness, µm
mately50HRC)shallnotbeplatedbyelectrodepositionunless
25 25
authorized by the purchaser.
12 12
88 6.3 Stress Relief—Steel parts having an ultimate tensile
strength of 1050 MPa (approximately 35 HRC) and above, and
that have been machined, ground, cold-formed, or cold-
NOTE 2—Cadmium coatings thicker than 12 µm are normally not
economical. straightened shall be heat-treated at 190 6 15°C for 5 h or
more for stress relief before cleaning and coating.
4.2 Types—Electrodeposited cadmium coatings shall be
6.4 Preparatory Procedures—The basis metal shall be sub-
identified by types on the basis of supplementary treatment
jected to such cleaning procedures as necessary to ensure a
required as follows:
surface satisfactory for subsequent electroplating. Materials
4.2.1 Type I—As electrodeposited without supplementary
used for cleaning shall have no damaging effects on the basis
treatment.
metal resulting in pits, intergranular attack, stress corrosion
4.2.2 Type II—With supplementary colored chromate treat-
cracking, or hydrogen embrittlement. If necessary, cleaning
ment.
materialsforsteelpartsshouldbeevaluatedinaccordancewith
4.2.3 Type III—With supplementary colorless chromate
Method F 519.
treatment.
NOTE 4—Forbasismetalpreparation,thefollowingstandardsshouldbe
employeddependinguponthemetallurgicalcomposition:PracticesB 183,
B 242, B 253, B 254, B 281, B 320, B 322, B 343 and B 558.
Annual Book of ASTM Standards, Vol 03.01.
6.5 Substrate—Cadmium shall be deposited directly on the
Annual Book of ASTM Standards, Vol 15.03.
Available from U.S. Government Printing Office, Washington DC 20402.
basis metal part without an undercoat of another metal except
Available from American National Standards Institute, 25 W. 43rd St., 4th
when the part is either stainless steel or aluminum and its
Floor, New York, NY 10036.
alloys.An undercoat of nickel is permissible on stainless steel.
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. With aluminum and aluminum alloys, the oxide layer shall be
B 766 – 86 (2003)
removed and replaced by a metallic zinc layer in accordance 7.1.1 The thickness of the coating everywhere on the
with Guide B 253. For better adherence, a copper strike or a significant surfaces shall conform to the requirements of the
nickel coating may be applied to the zinc layer before specified class, as defined in 4.1.
electroplating with the cadmium. 7.1.2 Significant surfaces are those normally visible (di-
6.6 Plating Process—The plating shall be applied after all
rectly or by reflection) that are essential to the appearance or
basis metal heat treatments and mechanical operations, such as serviceabilityofthearticlewhenassembledinnormalposition;
machining, brazing, welding, forming, and perforating of the
or that can be the source of corrosion products that will deface
article, have been completed. visible surfaces on the assembled article. When necessary, the
6.7 Hydrogen Embrittlement Relief— Steel parts having a
significant surfaces shall be indicated by the purchaser on
tensile strength of 1200 MPa (approximately 38 HRC) and applicable drawing of the article, or by the provision of
higher shall be baked at 190 6 15°C for8hor more within 4 suitably marked samples.
h after electroplating to provide hydrogen embrittlement relief.
NOTE 7—As heavier coatings are required for satisfactory corrosion
Electroplatedspringsandotherpartssubjecttoflexureshallnot
resistance than Class 5, allowance should be made in the fabrication of
be flexed, loaded, or used before the hydrogen embrittlement
most threaded articles, such as nuts, bolts, and similar fasteners with
relief treatment. The baking treatment for hydrogen embrittle-
complementary threads for dimensional tolerances to obtain necessary
ment relief shall be done before the application of any coatingbuild-up.Flatsurfacesandcertainshieldedorrecessedareas,such
as root-diameter of threads, have a tendency to exhibit lack of build-up
supplementary chromate treatment. When specified, freedom
and to be heavier at exposed edges and sharp projections with electrode-
from embrittlement shall be determined.
posited coatings. This trend is also found with vacuum-deposited cad-
NOTE 5—For high-strength steels, greater than 1300 MPa or approxi- mium coatings and is in direct contrast with mechanically deposited
mately 40 HRC, it is strongly recommended that the baking time be coatings.
extended to 23 h or more to ensure hydrogen embrittlement relief.
NOTE 8—The coating thickness requirements of this specification is a
NOTE 6—Electroplated steel parts, passivated by the baking operation
minimum requirement. Variation in thickness from point to point on an
for hydrogen embrittlement relief, require reactivation before the chro-
article is inherent in electroplating. Therefore, the thickness will have to
mate treatment. This application, immersion in a dilute acid solution,
exceed the specified value at some points on the significant surfaces to
should be done as soon as practical. If the chromating solution contains
ensure that it equals or exceeds the specified value at all points. Hence, in
sulfuric acid, then the reactivating solution should be 1 part of sulfuric
most cases, the average coating thickness of an article will be greater than
acid (sp gr 1.83) by volume added to 99 parts of water. If the chromating
the specified value; how much greater is largely determined by the shape
solution contains hydrochloric acid, then the reactivating solution should
of the article (see Practice B 507) and the characteristics of the electro-
be 1 part of hydrochloric acid (sp gr 1.16) by volume added to 99 parts of
plating process. In addition, the average coating thickness on articles will
water. Duration of immersion should be as brief as is consistent with the
vary from article to article within a production lot. Therefore, if all of the
nature of the work. Separately racked items can be reactivated in
articles in a production lot are to meet the thickness requirement, the
approximately 5 s, whereas a perforated container of barrel-plated parts
average coating thickness for the production lot as a whole will be greater
requires approximately 15 s.
than the average necessary to assure that a single article meets the
requirement.
6.8 Chromate Treatment:
6.8.1 Chromate treatments forTypes II and III shall be done
7.1.3 For nonsignificant visible surfaces, the minimum
in or with special aqueous acidic solutions composed of
thickness for Classes 25 and 12 shall be Class 8 (8 µm); for
hexavalent chromium along with certain anions that act as
Class 8 it shall be Class 5 (5 µm); and for Class 5 it shall be 4
catalyst or film-forming compounds to produce a continuous
µm.
smooth protective film. Chromic acid and nitric acid bright
7.2 Adhesion—The cadmium coating shall be sufficiently
dips shall not be used for treatment to produce chromate
adherent to the basis metal to pass the tests detailed in 10.2.
coatings. When proprietary materials are used for this treat-
7.3 Abrasion Resistant—The supplementary Type II chro-
ment, the instructions of the supplier should be followed.
matefilmshallbeadherent,nonpowdery,andabrasionresistant
6.8.2 The Type II film color shall range from an iridescent
(10.3)
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