ASTM B766-86(2008)
(Specification)Standard Specification for Electrodeposited Coatings of Cadmium
Standard Specification for Electrodeposited Coatings of Cadmium
ABSTRACT
This specification covers the requirements for electrodeposited cadmium coatings on products of iron, steel, and other metals. 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.Electrodeposited cadmium coatings shall be classified on the basis of thickness as Class 25, 12, 8, and 5. The coating shall be essentially pure cadmium produced by electrodeposition usually from an alkaline cyanide solution. The basis metal shall be subjected to such cleaning procedures as necessary to ensure a surface satisfactory for subsequent electroplating. Cadmium shall be deposited directly on the basis metal part without an undercoat of another metal except when the part is either stainless steel or aluminum and its alloys. The plating shall be applied after all basis metal heat treatments and mechanical operations. The thickness of the coating everywhere on the significant surface shall conform to the requirements of the specified class. The cadmium coating shall be sufficiently adherent to the basis metal to pass the tests. The supplementary Type II chromate film shall be adherent, nonpowdery, and abrasion resistant. The thickness of electrodeposited cadmium coatings shall be determined by the applicable test methods.
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.
General Information
Relations
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:B766 −86(Reapproved 2008)
Standard Specification for
Electrodeposited Coatings of Cadmium
This standard is issued under the fixed designation B766; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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 Department of Defense.
1. Scope products on the surface. This allows for proper functioning
during corrosive exposure of moving parts, threaded
1.1 Thisspecificationcoverstherequirementsforelectrode-
assemblies, valves, and delicate mechanisms without jamming
posited cadmium coatings on products of iron, steel, and other
with 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 Thefollowingstandardsformapartofthisdocumentto
beryllium copper, copper, nickel, and powder metallurgy parts.
the extent referenced herein.
1.2 Thecoatingisprovidedinvariousthicknessesuptoand
2.2 ASTM Standards:
including 25 µm either as electrodeposited or with supplemen-
A165Specification for Electrodeposited Coatings of Cad-
tary finishes.
mium on Steel (Withdrawn 1987)
1.3 Cadmiumcoatingsareusedforcorrosionresistanceand
B117Practice for Operating Salt Spray (Fog) Apparatus
for corrosion prevention of the basis metal part. The as-
B183Practice 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
B201Practice 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
B242Guide for Preparation of High-Carbon Steel for Elec-
the supplementary chromate finishes (Types II and III) on the
troplating
electroplated cadmium is to increase corrosion resistance.
B253Guide for Preparation of Aluminum Alloys for Elec-
Chromating will retard or prevent the formation of white
troplating
corrosionproductsonsurfacesexposedtovariousenvironmen-
B254Practice for Preparation of and Electroplating on
talconditionsaswellasdelaytheappearanceofcorrosionfrom
Stainless Steel
the basis metal.
B281Practice for Preparation of Copper and Copper-Base
1.4 Cadmium plating is used to minimize bi-metallic corro-
Alloys for Electroplating and Conversion Coatings
sionbetweenhigh-strengthsteelfastenersandaluminuminthe
B320Practice for Preparation of Iron Castings for Electro-
aerospaceindustry.Undercuttingofthreadsonfastenerpartsis
plating
not necessary as the cadmium coating has a low coefficient of
B322Guide for Cleaning Metals Prior to Electroplating
friction that reduces the tightening torque required and allows
B343Practice for Preparation of Nickel for Electroplating
repetitive dismantling.
with Nickel
B374Terminology Relating to Electroplating
1.5 Cadmium-coated parts can easily be soldered without
B487Test Method for Measurement of Metal and Oxide
the use of corrosive fluxes. Cadmium-coated steel parts have a
Coating Thickness by Microscopical Examination of
lower electrical contact resistance than zinc-coated steel. The
Cross Section
lubricity of cadmium plating is used on springs for doors and
B499Test Method for Measurement of CoatingThicknesses
latchesandforweavingmachineryoperatinginhighhumidity.
by the Magnetic Method: Nonmagnetic Coatings on
Corrosion products formed on cadmium are tightly adherent.
Magnetic Basis Metals
Unlike zinc, cadmium does not build up voluminous corrosion
1 2
This specification is under the jurisdiction of ASTM Committee B08 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
B08.06 on Soft Metals. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Aug. 1, 2008. Published September 2008. Originally the ASTM website.
approved in 1986. Last previous edition approved in 2003 as B766–86 (2003). The last approved version of this historical standard is referenced on
DOI: 10.1520/B0766-86R08. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B766−86 (2008)
NOTE 3—It is strongly recommended that production items be pro-
B504Test Method for Measurement of Thickness of Metal-
cessed as either Type II or Type III.
lic Coatings by the Coulometric Method
B507Practice for Design ofArticles to Be Electroplated on
5. Ordering Information
Racks
5.1 In order to make the application of this specification
B558Practice for Preparation of Nickel Alloys for Electro-
complete, the purchaser needs to supply the following infor-
plating
mation to the seller in the purchase order or other governing
B567Test Method for Measurement of Coating Thickness
document:
by the Beta Backscatter Method
5.1.1 The name, designation, and date of issue of this
B568Test Method for Measurement of Coating Thickness
specification.
by X-Ray Spectrometry
5.1.2 Deposit by class and type (4.1 and 4.2).
B571Practice for Qualitative Adhesion Testing of Metallic
5.1.3 Composition and metallurgical condition of the sub-
Coatings
strate to be coated. Application to high-strength steel parts
B602Test Method for Attribute Sampling of Metallic and
(6.2).
Inorganic Coatings
5.1.4 Heat treatment for stress relief, whether it has been
B697Guide for Selection of Sampling Plans for Inspection
performed or is required (6.3).
of Electrodeposited Metallic and Inorganic Coatings
5.1.5 Additional undercoat, if required (6.5).
E8Test Methods for Tension Testing of Metallic Materials
5.1.6 Plating process variation, if required (6.6).
F519Test Method for Mechanical Hydrogen Embrittlement
5.1.7 Hydrogen embrittlement relief, if required (6.7).
Evaluation of Plating/Coating Processes and Service En-
5.1.8 Desired color of the Type II film (6.8.2).
vironments
5.1.9 Location of significant surfaces (7.1.2).
2.3 Federal Standard:
5.1.10 Coating luster (7.5).
QQ-P-416Plating, Cadmium (Electrodeposited)
5.1.11 Whethernon-destructiveordestructivetestsaretobe
2.4 International Standard: used in cases of choice (Note 14).
ISO 2082 Metallic Coatings—Electroplated Coatings of
5.1.12 Configuration, procedures, and tensile load for hy-
Cadmium on Iron or Steel
drogen embrittlement relief test (9.4, 10.6, Supplementary
Requirements S2, and S3).
2.5 Military Standard:
5.1.13 Whether certification is required (Section 12).
MIL-STD-1312Fasteners, Test Methods
5.1.14 Whether supplementary requirements are applicable.
3. Terminology
6. Materials and Manufacture
3.1 Definitions—Definitions of terms used in this specifica-
6.1 NatureofCoating—Thecoatingshallbeessentiallypure
tion are in accordance with Terminology B374.
cadmium produced by electrodeposition usually from an alka-
line cyanide solution.
4. Classification
6.2 High Tensile Strength Steel Parts—Steelpartshavingan
4.1 Classes—Electrodeposited cadmium coatings shall be
ultimatetensilestrengthgreaterthan1650MPa(approximately
classified on the basis of thickness as follows:
50 HRC) shall not be plated by electrodeposition unless
Class Minimum Thickness, µm
authorized by the purchaser.
25 25
6.3 Stress Relief—Steel parts having an ultimate tensile
12 12
strengthof1050MPa(approximately35HRC)andabove,and
that have been machined, ground, cold-formed, or cold-
straightened shall be heat-treated at 190 6 15°C for 5 h or
NOTE 2—Cadmium coatings thicker than 12 µm are normally not
more for stress relief before cleaning and coating.
economical.
6.4 Preparatory Procedures—The basis metal shall be sub-
4.2 Types—Electrodeposited cadmium coatings shall be
jected to such cleaning procedures as necessary to ensure a
identified by types on the basis of supplementary treatment
surface satisfactory for subsequent electroplating. Materials
required as follows:
used for cleaning shall have no damaging effects on the basis
4.2.1 Type I—As electrodeposited without supplementary
metal resulting in pits, intergranular attack, stress corrosion
treatment.
cracking, or hydrogen embrittlement. If necessary, cleaning
4.2.2 Type II—With supplementary colored chromate treat-
materialsforsteelpartsshouldbeevaluatedinaccordancewith
ment.
Method F519.
4.2.3 Type III—With supplementary colorless chromate
treatment.
NOTE4—Forbasismetalpreparation,thefollowingstandardsshouldbe
employeddependinguponthemetallurgicalcomposition:PracticesB183,
B242, B253, B254, B281, B320, B322, B343, and B558.
Available from U.S. Government Printing Office, Washington DC 20402.
6.5 Substrate—Cadmium shall be deposited directly on the
Available from American National Standards Institute, 25 W. 43rd St., 4th
basis metal part without an undercoat of another metal except
Floor, New York, NY 10036.
when the part is either stainless steel or aluminum and its
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. alloys.An undercoat of nickel is permissible on stainless steel.
B766−86 (2008)
With aluminum and aluminum alloys, the oxide layer shall be 7. Coating Requirements
removed and replaced by a metallic zinc layer in accordance
7.1 Thickness:
with Guide B253. For better adherence, a copper strike or a
7.1.1 The thickness of the coating everywhere on the
nickel coating may be applied to the zinc layer before
significant surfaces shall conform to the requirements of the
electroplating with the cadmium.
specified class, as defined in 4.1.
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
basismetalheattreatmentsandmechanicaloperations,suchas
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.
hafterelectroplatingtoprovidehydrogenembrittlementrelief.
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-
mium coatings and is in direct contrast with mechanically deposited
NOTE 5—For high-strength steels, greater than 1300 MPa or approxi-
coatings.
mately 40 HRC, it is strongly recommended that the baking time be
NOTE 8—The coating thickness requirements of this specification is a
extended to 23 h or more to ensure hydrogen embrittlement relief.
minimum requirement. Variation in thickness from point to point on an
NOTE 6—Electroplated steel parts, passivated by the baking operation
article is inherent in electroplating. Therefore, the thickness will have to
for hydrogen embrittlement relief, require reactivation before the chro-
exceed the specified value at some points on the significant surfaces to
mate treatment. This application, immersion in a dilute acid solution,
ensure that it equals or exceeds the specified value at all points. Hence, in
should be done as soon as practical. If the chromating solution contains
mostcases,theaveragecoatingthicknessofanarticlewillbegreaterthan
sulfuric acid, then the reactivating solution should be 1 part of sulfuric
the specified value; how much greater is largely determined by the shape
acid (sp gr 1.83) by volume added to 99 parts of water. If the chromating
of the article (see Practice B507) and the characteristics of the electro-
solution contains hydrochloric acid, then the reactivating solution should
plating process. In addition, the average coating thickness on articles will
be1part ofhydrochloricacid(spgr1.16)byvolumeaddedto 99 parts of
vary from article to article within a production lot. Therefore, if all of the
water. Duration of immersion should be as brief as is consistent with the
articles in a production lot are to meet the thickness requirement, the
nature of the work. Separately racked items can be reactivated in
averagecoatingthicknessfortheproductionlotasawholewillbegreater
approximately 5 s, whereas a perforated container of barrel-plated parts
than the average necessary to assure that a single article meets the
requires approximately 15 s.
requirement.
6.8 Chromate Treatment: 7.1.3 For nonsignificant visible surfaces, the minimum
thickness for Classes 25 and 12 shall be Class 8 (8 µm); for
6.8.1 ChromatetreatmentsforTypesIIandIIIshallbedone
Class 8 it shall be Class 5 (5 µm); and for Class 5 it shall be 4
in or with special aqueous acidic solutions composed of
µm.
hexavalent chromium along with certain anions that act as
catalyst or film-forming compounds to produce a continuous
7.2 Adhesion—The cadmium coating shall be sufficiently
smooth protective film. Chromic acid and nitric acid bright
adherent to the basis metal to pass the tests detailed in 10.2.
dips shall not be used for treatment to produce chromate
7.3 Abrasion Resistant—The supplementary Type II chro-
coatings. When proprietary materials are used for this
matefilmshallbeadherent,nonpowdery,andabrasionresistant
treatment, the instructions of the supplier should be followed.
(10.3).
6.8.2 The Type II film color shall range from an iridescent
7.4 Corrosion Resistance—Cadmium coatings with supple-
yelloworathicker,moreprotec
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.