ASTM B994/B994M-22

Standard Specification for Nickel-Cobalt Alloy Coating

ABSTRACT
This specification outlines the requirements for corrosion-resistant coatings of electrodeposited nickel-cobalt on metallic substrates and electrodeposited nickel-cobalt used for electroforming. It includes an accelerated exposure test method to evaluate the effects of corrosion and galling on the nickel-cobalt alloy coating, as well as a means of reporting the results to the purchaser.
This specification incorporates a classification scheme that establishes service condition by thickness, classes of deposits based on the level of monitoring, and type based on supplemental coatings used after deposition. It also provides requirements for materials and manufacture; acceptance tests in terms of appearance, adhesion, and coating thickness, qualification tests (galling test, chemical composition, hydrogen embrittlement test, corrosion testing, environmental testing, third party reports, frequency of qualification tests); sampling; rejection; and certification.
SCOPE
1.1 This specification describes the requirements for corrosion-resistant coatings of electrodeposited nickel-cobalt on metallic substrates and electrodeposited nickel-cobalt used for electroforming.
Note 1: The nickel-cobalt alloy is principally deposited as a coating on steel products. It can also be electrodeposited on iron, stainless steel, aluminum, titanium, and any other metal substrate.
Note 2: The nickel-cobalt alloy coating has a low coefficient of friction of 0.08 that provides a dry lubricant on part surfaces that are in contact with each other and are subject to galling.  
1.2 This specification incorporates an accelerated exposure test method to evaluate the effects of corrosion and galling on the coating, and incorporates a means of reporting the results to the purchaser.  
1.3 The specification incorporates a classification scheme that establishes service conditions for thickness, classes of deposits based on the level of monitoring, and type based on supplemental coatings used after deposition.  
1.4 The coating thickness ranges from 5 to >30 μm, and it can be applied to machined parts, springs, latches, threaded parts, fasteners, etc. The deposit can also be used to electroform parts requiring high strength with the alloy being maintained at 50 % nickel-cobalt.  
1.5 The nickel-cobalt alloy is used to protect ferrous metals in contact with corrosive environments such as: oil and gas production facilities, coastal marine, and ACQ (Alkaline Copper Quaternary) treatments for wood treatments.  
1.6 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.7 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.8 This standard has been revised to comply with the Restriction of Hazardous Substances RoHS Requirements that seek to limit the exposure of workers and the public to toxic metals. The nickel-cobalt alloy does not contain any of the six Restricted Hazardous Substances.  
1.9 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.

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.03 - Engineering Coatings

Relations

• Refers: ASTM A193/A193M-24 - Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications
• Effective Date: 01-Mar-2024
• Refers: ASTM F1470-24 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 01-Jan-2024
• Refers: ASTM F519-23 - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 01-Dec-2023
• Refers: ASTM E2465-23 - Standard Test Method for Analysis of Ni-Base Alloys by Wavelength Dispersive X-Ray Fluorescence Spectrometry
• Effective Date: 01-Nov-2023
• Refers: ASTM B571-23 - Standard Practice for Qualitative Adhesion Testing of Metallic Coatings
• Effective Date: 01-Nov-2023
• Refers: ASTM B849-02(2023) - Standard Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
• Effective Date: 01-Nov-2023
• Refers: ASTM A194/A194M-20 - Standard Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High Temperature Service, or Both
• Effective Date: 01-May-2020
• Refers: ASTM G85-19 - Standard Practice for Modified Salt Spray (Fog) Testing
• Effective Date: 01-Nov-2019
• Refers: ASTM E2465-19 - Standard Test Method for Analysis of Ni-Base Alloys by Wavelength Dispersive X-Ray Fluorescence Spectrometry
• Effective Date: 01-Oct-2019
• Refers: ASTM B320-60(2019) - Standard Practice for Preparation of Iron Castings for Electroplating
• Effective Date: 01-Apr-2019
• Refers: ASTM B849-02(2019) - Standard Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
• Effective Date: 01-Apr-2019
• Refers: ASTM F519-18 - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 01-Nov-2018
• Refers: ASTM B571-18 - Standard Practice for Qualitative Adhesion Testing of Metallic Coatings
• Effective Date: 01-Aug-2018
• Refers: ASTM F1470-18 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 01-Feb-2018
• Refers: ASTM F519-17a - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 01-Dec-2017

Overview

ASTM B994/B994M-22 sets forth the requirements for corrosion-resistant coatings of electrodeposited nickel-cobalt alloy on metallic substrates, as well as for the use of nickel-cobalt in electroforming applications. Developed by ASTM International, this standard is widely adopted for enhancing the durability and functional performance of machined components, fasteners, springs, latches, and similar hardware exposed to corrosive environments. The nickel-cobalt alloy coating offers a low coefficient of friction, acting as a dry lubricant especially where galling resistance is critical, such as in threaded connections.

The specification addresses the need for reliable protective coatings in industries like oil and gas, marine, and heavy manufacturing, with focus on coating quality, thickness, chemical composition, adhesion, and resistance to corrosion and hydrogen embrittlement. The standard supports compliance with global environmental requirements, notably the RoHS directive, ensuring no restricted hazardous substances are present in the coating.

Key Topics

• Corrosion Resistance: The nickel-cobalt alloy coating is principally used on steel, iron, stainless steel, aluminum, titanium, and other metallic substrates, providing robust resistance to harsh environments.
• Low Friction and Galling Resistance: The alloy’s low coefficient of friction (around 0.08) reduces wear and prevents galling in mechanical assemblies where metal-to-metal contact occurs.
• Classification System:
  • Service Condition (SC): Specifies required coating thicknesses based on environment and mechanical demands (e.g., SC5 for slightly corrosive, SC25 for highly corrosive conditions).
  • Class: Defines the testing and monitoring rigor, ranging from comprehensive process verification to more basic checks.
  • Type: Indicates whether a supplemental treatment is used post-coating, such as lubricants or adhesives, tailored to the application need.
• Test Methodologies: Includes accelerated exposure, galling tests, corrosion and adhesion assessments, as well as hydrogen embrittlement testing.
• Regulatory Compliance: Designed to comply with RoHS restrictions, helping manufacturers meet worker and public safety regulations.

Applications

ASTM B994/B994M-22 is essential for sectors where corrosion protection and operational reliability are paramount. Typical uses include:

• Oil and Gas Equipment: Protects steel parts, fasteners, and connectors subject to ACQ-treated environments and high humidity.
• Coastal and Marine Engineering: Shields metallic components against saltwater corrosion, extending service life for critical infrastructure.
• Manufacturing of Springs, Fasteners, and Latches: Ensures consistent function and disassembly even after extended service.
• High-Strength Electroformed Parts: Supports the production of precision components needing both strength and corrosion resistance.
• Threaded Assemblies: Minimizes risk of seizure or galling during assembly and disassembly, important in maintenance-intensive environments.

By following this specification, manufacturers benefit from standardized procedures that optimize product longevity, reduce maintenance costs, and support traceability and quality control. The requirements for test reporting, sampling, and certification provide a framework to demonstrate conformance to end-users and regulatory bodies.

Related Standards

The specification references several other ASTM and ISO standards to ensure a comprehensive approach to surface preparation, coating application, and testing, including:

• ASTM B117 – Salt Spray (Fog) Testing
• ASTM B254, B320, B322 – Preparation and Cleaning of Metal Substrates
• ASTM B368, G85, G59 – Accelerated Corrosion and Electrochemical Testing
• ASTM B849, B850 – Pre- and Post-Treatments to Minimize Hydrogen Embrittlement
• ASTM F519 – Hydrogen Embrittlement Evaluation
• ASTM E2465 – X-Ray Fluorescence Analysis of Nickel-Based Alloys
• ISO/IEC 17025 – General Requirements for Testing and Calibration Laboratories

For professionals seeking to implement robust, corrosion-resistant nickel-cobalt alloy coatings, ASTM B994/B994M-22 serves as an essential reference, enabling products to meet high standards of durability, safety, and regulatory compliance.

Keywords: nickel-cobalt alloy, corrosion-resistant coating, galling, electrodeposited coating, fasteners, industrial coatings, ASTM B994/B994M-22, RoHS, hydrogen embrittlement, salt spray testing, standard specification, protective coatings.

Standards Content (Sample)

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.
Designation:B994/B994M −22
Standard Specification for
Nickel-Cobalt Alloy Coating
This standard is issued under the fixed designation B994/B994M; 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* responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This specification describes the requirements for
mine the applicability of regulatory limitations prior to use.
corrosion-resistant coatings of electrodeposited nickel-cobalt
1.8 This standard has been revised to comply with the
on metallic substrates and electrodeposited nickel-cobalt used
Restriction of Hazardous SubstancesRoHSRequirements that
for electroforming.
seek to limit the exposure of workers and the public to toxic
NOTE 1—The nickel-cobalt alloy is principally deposited as a coating
metals. The nickel-cobalt alloy does not contain any of the six
on steel products. It can also be electrodeposited on iron, stainless steel,
Restricted Hazardous Substances.
aluminum, titanium, and any other metal substrate.
NOTE 2—The nickel-cobalt alloy coating has a low coefficient of 1.9 This international standard was developed in accor-
friction of 0.08 that provides a dry lubricant on part surfaces that are in
dance with internationally recognized principles on standard-
contact with each other and are subject to galling.
ization established in the Decision on Principles for the
1.2 This specification incorporates an accelerated exposure
Development of International Standards, Guides and Recom-
test method to evaluate the effects of corrosion and galling on
mendations issued by the World Trade Organization Technical
thecoating,andincorporatesameansofreportingtheresultsto
Barriers to Trade (TBT) Committee.
the purchaser.
2. Referenced Documents
1.3 The specification incorporates a classification scheme
2.1 ASTM Standards:
that establishes service conditions for thickness, classes of
A193/A193M Specification for Alloy-Steel and Stainless
deposits based on the level of monitoring, and type based on
Steel Bolting for High Temperature or High Pressure
supplemental coatings used after deposition.
Service and Other Special Purpose Applications
1.4 The coating thickness ranges from 5 to >30 µm, and it
A194/A194M Specification for Carbon Steel, Alloy Steel,
can be applied to machined parts, springs, latches, threaded
and Stainless Steel Nuts for Bolts for High Pressure or
parts, fasteners, etc. The deposit can also be used to electro-
High Temperature Service, or Both
form parts requiring high strength with the alloy being main-
A681 Specification for Tool Steels Alloy
tained at 50 % nickel-cobalt.
B117 Practice for Operating Salt Spray (Fog) Apparatus
1.5 The nickel-cobalt alloy is used to protect ferrous metals
B183 Practice for Preparation of Low-Carbon Steel for
in contact with corrosive environments such as: oil and gas
Electroplating
production facilities, coastal marine, and ACQ (Alkaline Cop-
B242 Guide for Preparation of High-Carbon Steel for Elec-
per Quaternary) treatments for wood treatments.
troplating
B254 Practice for Preparation of and Electroplating on
1.6 Units—The values stated in either SI units or inch-
Stainless Steel
pound units are to be regarded separately as standard. The
B320 Practice for Preparation of Iron Castings for Electro-
values stated in each system are not necessarily exact equiva-
plating
lents; therefore, to ensure conformance with the standard, each
B322 Guide for Cleaning Metals Prior to Electroplating
system shall be used independently of the other, and values
B374 Terminology Relating to Electroplating
from the two systems shall not be combined.
B568 Test Method for Measurement of Coating Thickness
1.7 This standard does not purport to address all of the
by X-Ray Spectrometry
safety concerns, if any, associated with its use. It is the
B571 Practice for Qualitative Adhesion Testing of Metallic
Coatings
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.03 on Engineering Coatings. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2022. Published May 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2015. Last previous edition approved in 2015 as B994/B994M – 15. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/B0994_B0994M-22. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B994/B994M−22
B602 Guide for Attribute Sampling of Metallic and Inor- 4.3 Type—This number signifies the type of secondary
ganic Coatings treatment applied after the coating to modify the surface
B697 Guide for Selection of Sampling Plans for Inspection properties.
of Electrodeposited Metallic and Inorganic Coatings
NOTE 4—The type classification is used to identify supplemental
B762 GuideofVariablesSamplingofMetallicandInorganic
coating that enhances the performance in various applications. For
Coatings
qualification test purposes, if a supplemental coating is not used, that is
Type 0. Type 1 supplemental coatings are used to lock the threads or
B849 Specification for Pre-Treatments of Iron or Steel for
metal-to-metal contact points to increase the amount of energy needed to
Reducing Risk of Hydrogen Embrittlement
disassemble the junction.Type 2 supplemental coatings are used to reduce
B850 GuideforPost-CoatingTreatmentsofSteelforReduc-
the friction and aid in disassembly. Materials like gold, thallium, and
ing the Risk of Hydrogen Embrittlement
PTFE can be used to provide lubricity and reduce the break torque.
D1193 Specification for Reagent Water
4.3.1 Type 0 coatings are not treated with any supplemental
E2465 Test Method for Analysis of Ni-Base Alloys by
coatings.
WavelengthDispersiveX-RayFluorescenceSpectrometry
4.3.2 Type 1 coatings are treated with a material to secure
F519 Test Method for Mechanical Hydrogen Embrittlement
the coating to itself.
Evaluation of Plating/Coating Processes and Service En-
4.3.3 Type 2 coatings are treated with a material to reduce
vironments
the friction between coated surfaces.
F1470 Practice for Fastener Sampling for Specified Me-
chanical Properties and Performance Inspection
5. Ordering Information
G59 Test Method for Conducting Potentiodynamic Polariza-
5.1 Thepurchasershallspecifythefollowingwhenordering
tion Resistance Measurements
this coating:
G85 Practice for Modified Salt Spray (Fog) Testing
5.1.1 The specification number and revision year,
G102 Practice for Calculation of Corrosion Rates and Re-
5.1.2 The service condition, class, and type,
lated Information from Electrochemical Measurements
5.1.3 The significant surface on the part as identified on a
G193 Terminology and Acronyms Relating to Corrosion
drawing,
2.2 ISO Standard:
5.1.4 The base metal alloy designation under ASTM stan-
ISO/IEC 17025:2005 General Requirements for the Compe-
dard or equivalent,
tence of Testing and Calibration Laboratories
5.1.5 The tensile strength of the base metal in MPa,
5.1.6 Any supplemental requirements including Type 1 and
3. Terminology
Type 2 secondary treatments,
3.1 Definitions—Definitions of terms used in this specifica-
5.1.7 Any exception to stress relief prior to coating (see
tion are in accordance with Terminologies B374 and G193.
section 7.3),
5.1.8 Any exceptions to post anneal heat treatments (see
4. Classification
section 7.4),
4.1 The coatings of nickel-cobalt have been classified as
5.1.9 Any exceptions to tests specified in the acceptance
follows: service condition by thickness and type by secondary tests (see section 8), and
treatments.
5.1.10 Any exceptions to tests specified in the qualifications
tests (see section 9).
4.2 Service Condition (SC)—This number signifies the
5.1.11 Any special requirements of shot peening or location
thickness requirement based on the type of environment and
of rack or wire in the coating process, or both, should be
desired mechanical properties.
specified by the purchaser. Otherwise refer to 7.2.3 and 7.3.
NOTE 3—The 50 % NiCo alloy produces a high strength alloy that is
used in electroforming to manufacture parts. These deposits can be used
6. Coating Requirements
at various thicknesses ranging from 1 µm to hundreds of microns.
6.1 The coatings shall be nickel-cobalt alloy produced by
4.2.1 SC5 signifies that the application is slightly corrosive
electrodeposition.
and that a minimum 5 µm of coating is sufficient for protection
6.2 The nickel shall be in the range of 43 to 61% and the
and to provide the mechanical properties.
cobalt shall be in the range of 39 to 57%.
4.2.2 SC12 signifies that the application is mildly corrosive
and that a minimum 12 µm of coating is sufficient to protect
6.3 This coating shall be applied to the significant surface to
against corrosion and provide the mechanical properties.
the desired minimum thickness of the service condition.
4.2.3 SC18 signifies that the application is corrosive and
6.4 The coating shall meet all applicable requirements as
that a minimum of 18 µm of coating is sufficient to protect
established in the purchase order in accordance with Section 5.
against corrosion and provide the mechanical properties.
4.2.4 SC25 signifies that the application is corrosive and
7. Materials and Manufacture
thataminimum25µmofcoatingissufficienttoprotectagainst
7.1 Substrate—Defectsinthesurfaceofthebasismetalsuch
corrosion and provide the mechanical properties.
as scratches, porosity, pits, inclusions, roll and die marks, laps,
cracks, burrs, cold shuts, and roughness may adversely affect
the appearance and performance of the deposit, despite the
Available from International Organization for Standardization (ISO), 1, ch. de
la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org. observance of the best plating practice. Any such defects on
B994/B994M−22
significant surfaces shall be brought to the attention of the shall use Guide B850 to determine the appropriate heat
purchaser before plating.The producer shall not be responsible treatment for the steel based on its tensile strength.
for coatings defects resulting from surface conditions of the
8. Acceptance Tests
metal, if these conditions have been brought to the attention of
the purchaser.
8.1 These tests are performed on the article that has been
coated and can be performed by the producer prior to delivery
7.2 The substrate may be subjected to such polishing or
and by the purchaser upon delivery.
buffing operations as are necessary to yield deposits with the
desired final performance and appearance.
8.2 Appearance—The surface of the article shall be uniform
7.2.1 Peening—Peening prior to plating may be required on
in appearance, free of visible coating defects, such as blisters,
high-strength steel parts to induce residual compressive
pits, nodules, burning, cracks, or unplated areas, and other
stresses in the surface, which can reduce loss of strength and
defects that will affect the function of the coating.
improve stress corrosion resistance after plating.
8.3 Adhesion—The adhesion of the coating shall be such
7.2.2 Steel parts that are designed for unlimited life under
that when examined by one of the test methods described in
dynamic loads shall be shot peened or rotary flap peened.
Practice B571, it shall not show separation from the basis
NOTE 5—Controlled shot peening is the preferred method because there metal.
are geometries where rotary flap peening is not effective.
8.4 Coating Thickness—Coating thickness shall meet the
7.2.3 Unless otherwise specified, the shot peening shall be
minimum as specified in the purchase order by service condi-
accomplished on all surfaces for which the coating is required
tion.Useanappropriatemethodforthepart.TestMethodB568
andallimmediateadjacentsurfaceswhentheycontainnotches,
provides a rapid measurement of the mass per unit area of the
fillets, or other abrupt changes of section size where stresses
deposit.
will be concentrated.
9. Qualification Tests
7.3 Racking—Parts should be positioned so as to minimize
trapping of hydrogen gas in cavities and holes, allowing free
9.1 These tests are performed on the process to ensure the
circulation of solution over all surfaces to obtain uniform
system is capable of meeting the coating requirements. These
coating thickness. The location of rack or wire marks in the
tests shall be performed on SC25, Type 0 coupons at a
coating shall be agreed upon between the producer and
frequency established in Section 9.
purchaser.
9.2 Galling Test—The producer shall perform the galling
7.4 Cleaning of Basis Metal—Proper preparatory proce-
test in accordance with the procedures established in Appendix
dures and thorough cleaning of the basis metal are essential to
X1. The producer shall prepare the finishing lot galling report
ensure satisfactory adhesion and corrosion resistance perfor-
andshalldemonstratethatloadedspecimenswillpass600days
mance of the coating. It is recommended that the following
of evaluation with the torque ratio of less than 2.5. Frequency
appropriate standards be used: Practices B183, B254, and
of the Galling Test shall be every 120 days.
B320, and Guides B242 and B322.
9.3 Chemical Composition—Frequency of the chemical
7.5 Pretreatment—A suitable method shall activate the sur-
composition measurement shall be on every lot production by
face and remove oxide and foreign materials, which may cause using Test Method E2465 or other elemental analysis methods
poor adhesion and coating porosity.
that can be demonstrated to meet precision and bias require-
ments of better than 1 % mass weight.
7.6 Pretreatment of Iron or Steel for the Purpose of Reduc-
ing the Risk of Hydrogen Embrittlement—Allsteelpartshaving
9.4 Hydrogen Embrittlement Test—The producer shall per-
an ultimate tensile strength greater than 1000 MPa (31 HRC) form every 60 days, or more frequently, the procedure outlined
and that have been machined, ground, cold formed, or cold in Test Method F519 by processing a set of four standard 1a
straightened, shall be heat treated for stress relief to reduce the specimens. They shall pass Test Method F519 criteria of no
risk of hydrogen embrittlement in the part before clean and failure after 200 h at 75 % UTS.
electroplateprocesses.Iftheseheattreatmentsarenotrequired,
9.5 Corrosion Testing:
the purchaser shall specify in the ordering information SR-0. If
9.5.1 Electrochemical Corrosion Rate—The nickel-cobalt
the purchaser does not specify an SR-0 exception to heat
alloy coated article shall have a corrosion rate of less than
treatment, then the plater shall use Table 1 in Specification
0.8636 µm/y when tested under Test Method G59. Corrosion
B849 to determine the appropriate heat treatment for the steel
rate shall be calculated in accordance with Practice G102. The
based on its tensile strength.
test solution shall be prepared by dissolving 5 6 1 parts by
7.7 Post-Coating Treatments of Iron and Steel for the mass of sodium chloride in 95 parts of water conforming to
Purpose of Reducing the Risk of Hydrogen Embrittlement—All Type IV water in Specification D1193 (except that for this
electroplated steel parts having a tensile strength greater than practice, limits for chlorides and sodium may be ignored).
1000MPa(31HRC)aswellassurface-hardenedparts,shallbe Carefulattentionshouldbegiventothechemicalcontentofthe
baked to reduce the risk of hydrogen embrittlement. If these salt. The salt used shall be sodium chloride with not more than
heat treatments are not required, the purchaser shall specify in 0.3 % by mass of total impurities. Halides (bromide, fluoride,
the ordering information ER-0. If the purchaser does not and iodide) other than chloride shall constitute less than 0.1 %
specify an ER-0 exception to heat treatment, then the producer by mass of the salt content. Copper content shall be less than
B994/B994M−22
0.3 ppm by mass. Sodium chloride that has had anti-caking 10.6 An inspection lot shall be defined as a collection of
agents added shall not be used because such agents may act as coated articles that are the same kind, that have been produced
corrosion inhibitors. The level of pH shall be equal to 6.5 to to the same specification, that have been coated by a single
7.2, temperature 25 6 3° C, with atmospheric pressure and supplier at one time or approximately the same time, under
static conditions.The frequency of this shall be every 180 days essentially identical conditions, and that are submitted for
unless the purchaser specifies an
...

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: B994/B994M − 15 B994/B994M − 22
Standard Specification for
Nickel-Cobalt Alloy Coating
This standard is issued under the fixed designation B994/B994M; 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 Scope*
1.1 This specification describes the requirements for corrosion-resistant coatings of electrodeposited nickel-cobalt on metallic
substrates and electrodeposited nickel-cobalt used for electroforming.
NOTE 1—The nickel-cobalt alloy is principally deposited as a coating on steel products. It can also be electrodeposited on iron, stainless steel, aluminum,
titanium, and any other metal substrate.
NOTE 2—The nickel-cobalt alloy coating has a low coefficient of friction of 0.08 that provides a dry lubricant on part surfaces that are in contact with
each other and are subject to galling.
1.2 This specification incorporates an accelerated exposure test method to evaluate the effects of corrosion and galling on the
coating, and incorporates a means of reporting the results to the purchaser.
1.3 The specification incorporates a classification scheme that establishes service conditions for thickness, classes of deposits
based on the level of monitoring, and type based on supplemental coatings used after deposition.
1.4 The coating thickness ranges from 5 to >30 μm, and it can be applied to machined parts, springs, latches, threaded parts,
fasteners, etc. The deposit can also be used to electroform parts requiring high strength with the alloy being maintained at 50%50 %
nickel-cobalt.
1.5 The nickel-cobalt alloy is used to protect ferrous metals in contact with corrosive environments such as: oil and gas production
facilities, costalcoastal marine, and ACQ (Alkaline Copper Quaternary) treatments for wood treatments.
1.6 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.7 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.
1.8 This standard has been revised to comply with the Restriction of Hazardous Substances RoHS Requirements that seek to limit
the exposure of workers and the public to toxic metals. The nickel-cobalt alloy does not contain any of the six Restricted Hazardous
Substances.
This test method specification is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.03 on Engineering Coatings.
Current edition approved March 1, 2015May 1, 2022. Published March 2015May 2022. Originally approved in 2015. Last previous edition approved in 2015 as
B994/B994M – 15. DOI: 10.1520/B0994_B0994M–15.10.1520/B0994_B0994M-22.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B994/B994M − 22
1.9 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:
A193/A193M Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other
Special Purpose Applications
A194/A194M Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High
Temperature Service, or Both
A681 Specification for Tool Steels Alloy
B117 Practice for Operating Salt Spray (Fog) Apparatus
B183 Practice for Preparation of Low-Carbon Steel for Electroplating
B242 Guide for Preparation of High-Carbon Steel for Electroplating
B254 Practice for Preparation of and Electroplating on Stainless Steel
B320 Practice for Preparation of Iron Castings for Electroplating
B322 Guide for Cleaning Metals Prior to Electroplating
B368 Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
B374 Terminology Relating to Electroplating
B568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B571 Practice for Qualitative Adhesion Testing of Metallic Coatings
B602 Guide for Attribute Sampling of Metallic and Inorganic Coatings
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B762 Guide 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
D1193 Specification for Reagent Water
E2465 Test Method for Analysis of Ni-Base Alloys by Wavelength Dispersive X-Ray Fluorescence Spectrometry
F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
F1470 Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
G59 Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
G85 Practice for Modified Salt Spray (Fog) Testing
G102 Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements
G193 Terminology and Acronyms Relating to Corrosion
2.2 ISO Standard:
ISO/IEC 17025:2005 General Requirements for the Competence of Testing and Calibration Laboratories
3. Terminology
3.1 Definitions—Definitions of terms used in this specification are in accordance with Terminologies B374 and G193.
4. Classification
4.1 The coatings of nickel-cobalt have been classified as follows: service condition by thickness, class by test methods required,
thickness and type by secondary treatments.
4.2 Service Condition (SC)—This number signifies the thickness requirement based on the type of environment and desired
mechanical properties.
NOTE 3—The 50%50 % NiCo alloy produces a high strength alloy that is used in electroforming to manufacture parts. These deposits can be used at
various thicknesses ranging from 1 μm to hundreds of microns.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
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4.2.1 SC5 signifies that the application is slightly corrosive and that a minimum 5 μm of coating is sufficient for protection and
to provide the mechanical properties.
4.2.2 SC12 signifies that the application is mildly corrosive and that a minimum 12 μm of coating is sufficient to protect against
corrosion and provide the mechanical properties.
4.2.3 SC18 signifies that the application is corrosive and that a minimum of 18 μm of coating is sufficient to protect against
corrosion and provide the mechanical properties.
4.2.4 SC25 signifies that the application is corrosive and that a minimum 25 μm of coating is sufficient to protect against corrosion
and provide the mechanical properties.
4.3 Class—This number signifies the type and frequency of testing and monitoring programs that are used to control the process.
4.3.1 Class 1—Incorporates these standard tests: Galling (see Appendix X1) , Composition (see 9.3), Test Methods F519 and
B368, and Practices B117 and G85.
4.3.2 Class 2—Incorporates these standard tests: Composition (see 9.3), Test Methods F519 and B368, and Practices B117 and
G85.
4.3.3 Class 3—Incorporates these standard tests: Composition (see 9.3) and Practice B117.
4.3.4 Class 4—Incorporates the standard test of composition (see 9.3).
4.3 Type—This number signifies the type of secondary treatment applied after the coating to modify the surface properties.
NOTE 4—The type classification is used to identify supplemental coating that enhances the performance in various applications. For qualification test
purposes, if a supplemental coating is not used, that is Type 0. Type 1 supplemental coatings are used to lock the threads or metal-to-metal contact points
to increase the amount of energy needed to disassemble the junction. Type 2 supplemental coatings are used to reduce the friction and aid in disassembly.
Materials like gold, thallium, and PTFE can be used to provide lubricity and reduce the break torque.
4.3.1 Type 0 coatings are not treated with any supplemental coatings.
4.3.2 Type 1 coatings are treated with a material to secure the coating to itself.
4.3.3 Type 2 coatings are treated with a material to reduce the friction between coated surfaces.
5. Ordering Information
5.1 The purchaser shall specify the following when ordering this coating:
5.1.1 The specification number and revision year,
5.1.2 The service condition, class, and type,
5.1.3 The significant surface on the part as identified on a drawing,
5.1.4 The base metal alloy designation under ASTM standard or equivalent,
5.1.5 The tensile strength of the base metal in MPa,
5.1.6 Any supplemental requirements including Type 1 and Type 2 secondary treatments,
5.1.7 Any exception to stress relief prior to coating (see section 7.3),
5.1.8 Any exceptions to post anneal heat treatments (see section 7.4),
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5.1.9 Any exceptions to tests specified in the acceptance tests (see section 8), and
5.1.10 Any exceptions to tests specified in the qualifications tests (see section 9).
5.1.11 Any special requirements of shot peening or location of rack or wire in the coating process, or both, should be specified
by the purchaser. Otherwise refer to 7.2.3 and 7.3.
6. Coating Requirements
6.1 The coatings shall be nickel-cobalt alloy produced by electrodeposition.
6.2 The nickel shall be in the range of 43 to 61% and the cobalt shall be in the range of 39 to 57%.
6.3 This coating shall be applied to the significant surface to the desired minimum thickness of the service condition.
6.4 The coating shall meet all applicable requirements as established in the purchase order in accordance with Section 5.
7. Materials and Manufacture
7.1 Substrate—Defects in the surface of the basis metal such as scratches, porosity, pits, inclusions, roll and die marks, laps,
cracks, burrs, cold shuts, and roughness may adversely affect the appearance and performance of the deposit, despite the
observance of the best plating practice. Any such defects on significant surfaces shall be brought to the attention of the purchaser
before plating. The producer shall not be responsible for coatings defects resulting from surface conditions of the metal, if these
conditions have been brought to the attention of the purchaser.
7.2 The substrate may be subjected to such polishing or buffing operations as are necessary to yield deposits with the desired final
performance and appearance.
7.2.1 Peening—Peening prior to plating may be required on high-strength steel parts to induce residual compressive stresses in
the surface, which can reduce loss of strength and improve stress corrosion resistance after plating.
7.2.2 Steel parts that are designed for unlimited life under dynamic loads shall be shot peened or rotary flap peened.
NOTE 5—Controlled shot peening is the preferred method because there are geometries where rotary flap peening is not effective.
7.2.3 Unless otherwise specified, the shot peening shall be accomplished on all surfaces for which the coating is required and all
immediate adjacent surfaces when they contain notches, fillets, or other abrupt changes of section size where stresses will be
concentrated.
7.3 Racking—Parts should be positioned so as to minimize trapping of hydrogen gas in cavities and holes, allowing free circulation
of solution over all surfaces to obtain uniform coating thickness. The location of rack or wire marks in the coating shall be agreed
upon between the producer and purchaser.
7.4 Cleaning of Basis Metal—Proper preparatory procedures and thorough cleaning of the basis metal are essential to ensure
satisfactory adhesion and corrosion resistance performance of the coating. It is recommended that the following appropriate
standards be used: Practices B183, B254, and B320, and Guides B242 and B322.
7.5 Pretreatment—A suitable method shall activate the surface and remove oxide and foreign materials, which may cause poor
adhesion and coating porosity.
7.6 Pretreatment of Iron or Steel for the Purpose of Reducing the Risk of Hydrogen Embrittlement—All steel parts having an
ultimate tensile strength greater than 1000 MPa (31 HRC) and that have been machined, ground, cold formed, or cold straightened,
shall be heat treated for stress relief to reduce the risk of hydrogen embrittlement in the part before clean and electroplate processes.
If these heat treatments are not required, the purchaser shall specify in the ordering information SR-0. If the purchaser does not
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specify an SR-0 exception to heat treatment, then the plater shall use Table 1 in Specification B849 to determine the appropriate
heat treatment for the steel based on its tensile strength.
7.7 Post-Coating Treatments of Iron and Steel for the Purpose of Reducing the Risk of Hydrogen Embrittlement—All electroplated
steel parts having a tensile strength greater than 1000 MPa (31 HRC) as well as surface-hardened parts, shall be baked to reduce
the risk of hydrogen embrittlement. If these heat treatments are not required, the purchaser shall specify in the ordering information
ER-0. If the purchaser does not specify an ER-0 exception to heat treatment, then the producer shall use Guide B850 to determine
the appropriate heat treatment for the steel based on its tensile strength.
8. Acceptance Tests
8.1 These tests are performed on the article that has been coated and can be performed by the producer prior to delivery and by
the purchaser upon delivery.
8.2 Appearance—The surface of the article shall be uniform in appearance, free of visible coating defects, such as blisters, pits,
roughness, nodules, burning, cracks, or unplated areas, and other defects that will affect the function of the coating.
8.3 Adhesion—The adhesion of the coating shall be such that when examined by one of the test methods described in Practice
B571, it shall not show separation from the basis metal.
8.4 Coating Thickness—Coating thickness shall meet the minimum as specified in the purchase order by service condition. Use
an appropriate method for the part. Test Method B568 provides a rapid measurement of the mass per unit area of the deposit.
9. Qualification Tests
9.1 These tests are performed on the process to ensure the system is capable of meeting the coating requirements by class.
requirements. These tests shall be performed on SC25, Type 0 coupons at a frequency established in subsectionSection 9.89 based
on the class.
9.2 Galling Test—The producer shall perform the galling test in accordance with the procedures established in Appendix X1. The
producer shall prepare the finishing lot galling report and shall demonstrate that loaded specimens will pass 608600 days of
evaluation with the torque rationratio of less than 2.5. Frequency of the Galling Test shall be every 120 days.
9.3 Chemical Composition—The nickel-cobalt alloy composition shall be measured quarterly or more frequently as specified
Frequency of the chemical composition measurement shall be on every lot production by using Test Method E2465 or other
elemental analysis methods that can be demonstrated to meet precision and bias requirements of better than 1%1 % mass weight.
9.4 Hydrogen Embrittlement Test—The producer shall perform quarterly, every 60 days, or more frequently, the procedure outlined
in Test Method F519 by processing a set of four standard 1a specimens. They shall pass Test Method F519 criteria of no failure
after 200 hours 200 h at 75%75 % UTS.
9.5 Corrosion Testing:Corrosion Testing:
9.5.1 Electrochemical Corrosion Rate—The nickel-cobalt alloy coated article shall have a corrosion rate of less than 0.8636 μm/y
when tested under Test Method G59. Corrosion rate shall be calculated in accordance with Practice G102. The test solution shall
be prepared by dissolving 5 6 1 parts by mass of sodium chloride in 95 parts of water conforming to Type IV water in Specification
D1193 (except that for this practice, limits for chlorides and sodium may be ignored). Careful attention should be given to the
chemical content of the salt. The salt used shall be sodium chloride with not more than 0.3 % by mass of total impurities. Halides
(bromide, fluoride, and iodide) other than chloride shall constitute less than 0.1 % by mass of the salt content. Copper content shall
be less than 0.3 ppm by mass. Sodium chloride that has had anti-caking agents added shall not be used because such agents may
act as corrosion inhibitors. The level of pH shall be equal to 6.5 to 7.2, temperature 25 6 3° C, with atmospheric pressure and
static conditions. The frequency of this shall be quarterly every 180 days unless the purchaser specifies an increased frequency.
9.6 Environmental TestingEnvironmental Testing:
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9.6.1 CASS Test—The producer shall evaluate the process corrosion protection by performing Test Method B368 on test coupons
quarterly or more frequently as required. Panels processed to SC25 shall not show any red rust before 120 hours of exposure
9.6.1 Salt Spray (Fog) Test—The producer shall evaluate the process corrosion protection of the nickel-cobalt alloy by Practice
B117 quarterly or more frequently as specified. Panels processed to SC25 shall pass with no red rust before 500 hours 500 h of
exposure to salt spray (fog) as outlined in Prac
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