ASTM B607-21

Standard Specification for Autocatalytic Nickel Boron Coatings for Engineering Use

ABSTRACT
This standard contains the requirements for autocatalytic nickel boron alloy coatings deposited from aqueous solutions without the use of external electric sources. The specification classifies the hard, uniform, microporous, and limited corrosion protection coatings as either Type 1 or Type 2 depending on the boron content. Both the physical and mechanical properties of the coatings such as density, hardness, stress, and melting point also vary with the boron content. In general, these coatings are not heat treated to maintain solderability.
SCOPE
1.1 This specification describes the requirements for coatings of autocatalytic nickel boron deposited from aqueous solutions onto substrates for engineering (functional) use. The specification classifies these coatings into two types:  
1.1.1 Type 1 Coatings have a boron content of 0.1 to less than 3.5 mass percent with the balance nickel.  
1.1.2 Type 2 Coatings have a boron content of 3.5 to 6 mass percent and a minimum of 90 mass percent nickel.  
1.2 Nickel boron coatings are produced by autocatalytic (electroless) deposition from aqueous solutions. These solutions contain either an alkylamineborane or sodium borohydride as a reducing agent, a source of nickel ions, a buffer, complexant, and control chemicals.  
1.3 The coatings are hard and uniform in thickness, even on irregular shaped parts, and used in a wide range of applications.  
1.4 Process solutions formulated with an alkylamineborane usually produce coatings that contain 0.1 to 3.5 % boron. Thin coatings of this type provide bondability and solderability on electronic components such as lead frames, electrical contacts, and headers. To maintain solderability, these coatings are generally not heat treated.  
1.5 Process solutions formulated with sodium borohydride are strongly alkaline and are frequently used to plate steel and titanium parts to impart surface hardness and wear resistance properties. Deposits produced from these processes can contain 3 to 5 % boron and thallium or other metals which are used to stabilize the plating solution and modify the coating properties.  
1.6 The physical and mechanical properties of these deposits such as density, hardness, stress, and melting point will vary with the boron content. The variation of boron content also affects the quantity and structure of nickel boride precipitated during heat treatment. In the as-plated condition, the deposit consists of a predominantly amorphous mixture of nickel and boron with a hardness of about 700 HKN. When the deposit is heated above 300 °C, the nickel crystallizes, forming nickel clusters of Ni (111) and boron precipitates as nickel boride, Ni3B (211) and (311), increasing the hardness to greater than 1000 HK100 for Type 2 coatings.  
1.7 The nickel boron coatings are microporous and offer limited corrosion protection. Their columnar structure, however, is beneficial in reducing wear because it provides a means of trapping lubricants within the surface of the coated part.  
1.8 This document describes only autocatalytic nickel boron coatings that have been produced without use of external electric sources.  
1.9 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.10 The following hazards caveat pertains only to the Test Methods section of this specification:  This standard does not purport to address the safety problems 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.  
1.11 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 ...

General Information

• Status: Published
• Publication Date: 30-Sep-2021
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.03 - Engineering Coatings

Relations

• 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 B678-23 - Standard Test Method for Solderability of Metallic-Coated Products
• 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 D2714-94(2019) - Standard Test Method for Calibration and Operation of the Falex Block-on-Ring Friction and Wear Testing Machine
• Effective Date: 01-May-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 F519-17a - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 01-Dec-2017
• Refers: ASTM B678-86(2017) - Standard Test Method for Solderability of Metallic-Coated Products
• Effective Date: 01-Nov-2017
• Refers: ASTM F519-17 - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 01-Mar-2017
• Refers: ASTM D2670-95(2016) - Standard Test Method for Measuring Wear Properties of Fluid Lubricants (Falex Pin and Vee Block Method)
• Effective Date: 01-Jan-2016
• Refers: ASTM B667-97(2014) - Standard Practice for Construction and Use of a Probe for Measuring Electrical Contact Resistance
• Effective Date: 01-Oct-2014
• Refers: ASTM D2714-94(2014) - Standard Test Method for Calibration and Operation of the Falex Block-on-Ring Friction and Wear Testing Machine
• Effective Date: 01-May-2014
• Refers: ASTM B571-97(2013) - Standard Practice for Qualitative Adhesion Testing of Metallic Coatings
• Effective Date: 01-Dec-2013
• Refers: ASTM F519-13 - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 01-Dec-2013
• Refers: ASTM F519-12a - Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
• Effective Date: 15-Nov-2012

Overview

ASTM B607-21: Standard Specification for Autocatalytic Nickel Boron Coatings for Engineering Use provides comprehensive requirements for the deposition and classification of autocatalytic (electroless) nickel boron alloy coatings. These coatings are applied from aqueous solutions without the use of external electric sources, making them ideal for engineering applications where uniform, hard, and wear-resistant coatings are required. The standard defines two types of coatings based on their boron content and specifies relevant post-treatment classes and minimum thickness grades to meet various industrial performance needs.

Key Topics

• Coating Types:
  • Type 1: Boron content of 0.1 to <3.5 mass percent; the balance is nickel.
  • Type 2: Boron content of 3.5 to 6 mass percent, and at least 90 mass percent nickel.
• Deposition Process:
  • Utilizes autocatalytic (electroless) methods from aqueous solutions.
  • Reducing agents include alkylamineborane (produces Type 1) or sodium borohydride (produces Type 2).
• Physical and Mechanical Properties:
  • Hardness and density vary with boron content.
  • Uniform thickness distribution, even on complex or irregularly shaped substrates.
  • Increased hardness upon specific heat treatments.
  • Amorphous as-plated; can crystallize with heat, enhancing hardness and wear resistance.
• Post-Treatment Classes:
  • As-plated, or with heat treatments tailored for stress relief, hardness, improved adhesion, and hydrogen embrittlement relief, depending on substrate and application.
• Minimum Thickness Grades:
  • Ranges from 0.5 μm to 75 μm, supporting requirements from thin functional electronic finishes to robust wear surfaces.

Applications

Autocatalytic nickel boron coatings offer several practical advantages for engineering use:

• Wear Resistance:
  The coatings’ hard, microporous, and columnar structure enables excellent abrasion resistance and the ability to retain lubricants, reducing friction and extending part life.
• Corrosion Protection:
  While providing limited corrosion protection, the structure of these coatings helps trap lubricants and minimize wear, especially in moving or contacting parts.
• Uniform Coverage:
  The electroless process ensures even coating thickness on complex geometries, internal surfaces, and intricate parts.
• Electronic Components:
  Type 1 coatings, which are generally not heat treated, preserve solderability and bondability, making them well-suited for lead frames, contacts, and headers in electronics.
• Critical Mechanical Parts:
  Type 2 coatings are ideal for applications requiring enhanced hardness and wear resistance, such as tooling, steel, or titanium components in aerospace, automotive, and precision engineering sectors.
• Hydrogen Embrittlement Relief:
  Specific heat treatments are used for high-strength steel parts to prevent hydrogen embrittlement, supporting reliable performance in safety-critical components.

Related Standards

For quality assurance, performance testing, and compatibility with other coating and sampling standards, ASTM B607-21 references and harmonizes with several key documents:

• ASTM Standards:

  • ASTM B374: Terminology Relating to Electroplating
  • ASTM B487: Measurement of Coating Thickness by Microscopical Examination
  • ASTM B567: Thickness Measurement by Beta Backscatter
  • ASTM B568: Thickness Measurement by X-Ray Spectrometry
  • ASTM B571: Adhesion Testing of Metallic Coatings
  • ASTM B578: Microindentation Hardness Testing
  • ASTM B602: Sampling of Metallic and Inorganic Coatings
  • ASTM B678: Solderability Testing
  • ASTM D2670/D2714: Wear Testing of Fluid Lubricants
  • ASTM D4060: Abrasion Resistance Testing

• Aerospace Standards (for reference):

  • AMS 2399, AMS 2430, AMS 2433

• Government and International Sampling Standards:

  • ANSI/ASQ Z1.4: Sampling by Attributes
  • MIL-STD-1916: Product Acceptance Methods

Practical Value

ASTM B607-21 is essential for engineers, manufacturers, and quality control professionals involved with functional metal coatings. By applying the guidelines and requirements of this standard, organizations can ensure consistent performance, durability, and reliability of nickel boron coatings-which are critical for high-wear and high-precision industrial applications. Using ASTM B607-21 ensures process repeatability, facilitates compliance in procurement, and supports the production of high-quality coated components for demanding environments.

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:B607 −21
Standard Specification for
Autocatalytic Nickel Boron Coatings for Engineering Use
This standard is issued under the fixed designation B607; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* boron with a hardness of about 700 HKN. When the deposit is
heated above 300 °C, the nickel crystallizes, forming nickel
1.1 This specification describes the requirements for coat-
clusters of Ni (111) and boron precipitates as nickel boride,
ings of autocatalytic nickel boron deposited from aqueous
Ni B (211) and (311), increasing the hardness to greater than
solutions onto substrates for engineering (functional) use. The
1000 HK for Type 2 coatings.
specification classifies these coatings into two types:
1.1.1 Type 1 Coatings have a boron content of 0.1 to less 1.7 The nickel boron coatings are microporous and offer
than 3.5 mass percent with the balance nickel. limited corrosion protection. Their columnar structure,
1.1.2 Type 2 Coatings have a boron content of 3.5 to 6 mass however, is beneficial in reducing wear because it provides a
percent and a minimum of 90 mass percent nickel. means of trapping lubricants within the surface of the coated
part.
1.2 Nickel boron coatings are produced by autocatalytic
(electroless) deposition from aqueous solutions. These solu- 1.8 Thisdocumentdescribesonlyautocatalyticnickelboron
tions contain either an alkylamineborane or sodium borohy- coatings that have been produced without use of external
dride as a reducing agent, a source of nickel ions, a buffer, electric sources.
complexant, and control chemicals.
1.9 Units—The values stated in SI units are to be regarded
1.3 The coatings are hard and uniform in thickness, even on as standard. No other units of measurement are included in this
irregularshapedparts,andusedinawiderangeofapplications. standard.
1.10 The following hazards caveat pertains only to the Test
1.4 Process solutions formulated with an alkylamineborane
Methods section of this specification: This standard does not
usually produce coatings that contain 0.1 to 3.5 % boron. Thin
purport to address the safety problems associated with its use.
coatings of this type provide bondability and solderability on
It is the responsibility of the user of this standard to establish
electronic components such as lead frames, electrical contacts,
appropriate safety, health, and environmental practices and
and headers. To maintain solderability, these coatings are
determine the applicability of regulatory limitations prior to
generally not heat treated.
use.
1.5 Process solutions formulated with sodium borohydride
1.11 This international standard was developed in accor-
are strongly alkaline and are frequently used to plate steel and
dance with internationally recognized principles on standard-
titanium parts to impart surface hardness and wear resistance
ization established in the Decision on Principles for the
properties.Depositsproducedfromtheseprocessescancontain
Development of International Standards, Guides and Recom-
3 to 5 % boron and thallium or other metals which are used to
mendations issued by the World Trade Organization Technical
stabilizetheplatingsolutionandmodifythecoatingproperties.
Barriers to Trade (TBT) Committee.
1.6 The physical and mechanical properties of these depos-
itssuchasdensity,hardness,stress,andmeltingpointwillvary
2. Referenced Documents
with the boron content. The variation of boron content also
2.1 ASTM Standards:
affects the quantity and structure of nickel boride precipitated
B374 Terminology Relating to Electroplating
during heat treatment. In the as-plated condition, the deposit
B487 Test Method for Measurement of Metal and Oxide
consists of a predominantly amorphous mixture of nickel and
Coating Thickness by Microscopical Examination of
Cross Section
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 Oct. 1, 2021. Published October 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1991. Last previous edition approved in 2015 as B607 – 15. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0607-21. 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
B607−21
B567 Test Method for Measurement of Coating Thickness 2.3 ANSI Standard:
by the Beta Backscatter Method ANSI/ASQ Z1.4 Sampling Procedures and Tables for In-
B568 Test Method for Measurement of Coating Thickness spection by Attributes
by X-Ray Spectrometry
2.4 U.S. Government Standard:
B571 Practice for Qualitative Adhesion Testing of Metallic
MIL-STD-1916 DOD Preferred Methods for Acceptance of
Coatings
Product
B578 Test Method for Microhardness of Electroplated Coat-
ings
3. Terminology
B602 Test Method for Attribute Sampling of Metallic and
3.1 Definitions: Many terms used in this specification are
Inorganic Coatings
defined in Terminology B374.
B656 Guide for Autocatalytic (Electroless) Nickel-
3.2 Definitions of Terms Specific to This Standard:
Phosphorus Deposition on Metals for Engineering Use
3.2.1 cold shut, n—a void on the surface which has been
(Discontinued 2000) (Withdrawn 2000)
closed by machining and then partially opened through clean-
B667 Practice for Construction and Use of a Probe for
ing.
Measuring Electrical Contact Resistance
B678 Test Method for Solderability of Metallic-Coated
3.2.2 hot halide stress-corrosion cracking, n—a type of
Products
mechanical failure produced by halogenated solvents that have
B697 Guide for Selection of Sampling Plans for Inspection
been absorbed onto titanium and then in the presence of heat
of Electrodeposited Metallic and Inorganic Coatings
cause microcracking, and the loss of mechanical strength.
B762 Test Method of Variables Sampling of Metallic and
3.2.3 lap cracks, n—a surface imperfection caused by cold
Inorganic Coatings
working of steels producing a void which can be duplicated in
D2670 Test Method for Measuring Wear Properties of Fluid
the deposit.
Lubricants (Falex Pin and Vee Block Method)
3.2.4 significant surface, n—those substrate surfaces which
D2714 Test Method for Calibration and Operation of the
the coating must protect from corrosion or wear, or both, and
Falex Block-on-Ring Friction and Wear Testing Machine
that are essential to the appearance.
D4060 Test Method for Abrasion Resistance of Organic
Coatings by the Taber Abraser
4. Classification
E39 Methods for Chemical Analysis of Nickel (Withdrawn
4.1 The classification by type of these coatings establishes
1995)
the amount of boron in the alloy.
F519 Test Method for Mechanical Hydrogen Embrittlement
4.1.1 Type 1—Coatings shall contain 0.1 to less than 3.5
Evaluation of Plating/Coating Processes and Service En-
mass percent boron with the balance nickel.
vironments
4.1.2 Type 2—Coatings shall contain 3.5 to 6 mass percent
2.2 Aerospace Materials Specifications:
boron and a minimum of 90 mass percent nickel.
AMS 2399 Electroless Nickel-Boron Plating
AMS 2430 Shot Peening
4.2 The classification by class of these coatings establishes
AMS2433 Plating,Nickel-Thallium-BoronorNickel-Boron
the post treatment to be performed on the part(s). The post
Electroless Deposition
treatment steps are designed to reduce the potential for
hydrogen embrittlement, increase the adhesion of the coating
NOTE 1—AMS 2399 and AMS 2433 are not requirements, they are
to the substrate, improve the fatigue properties of the part(s),
referenced for information only.
and increase the wear resistance and hardness of the coating:
3 Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
The last approved version of this historical standard is referenced on
4th Floor, New York, NY 10036, http://www.ansi.org.
www.astm.org.
4 The original reference MIL-STD-105 Sampling Procedures and Tables for
Available from Society of Automotive Engineers (SAE), 400 Commonwealth
Inspection by Attributes was cancelled in February 2008 and referred to MIL-
Dr., Warrendale, PA 15096-0001, http://www.sae.org.
5 STD-1916 or ANSI/ASQ Z1.4.
The original reference MIL-S-13165, Shot Peening of Metal Parts was
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
cancelled in February 1998 and referred to SAE AMS-S-13165, which was also
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
cancelled and superseded by AMS 2430.
TABLE 1 Classification of Heat Treatment
Class Description Tensile strength steel, MPa Temperature (°C) Time (h), minimum
1 No Heat Treatment, As Plated
2 Increase Hardness 375 ± 10 1.5
3 Adhesion, Steel; Hydrogen 1000 to 1450 190 ± 15 2
Embrittlement Relief
1450 to 1800 190 ± 15 18
Over 1800 190 ± 15 23
4 Adhesion, Carburized Steel and Age 125±5 1
Hardened Aluminum
5 Adhesion, Titanium or Titanium Alloys 370 ± 5 4
B607−21
4.2.1 Class 1—Partsaresuppliedasplatedwithnopostheat 5.1.14 Supplemental solderability requirements (see S1.6).
treatment. 5.1.15 Supplemental U.S. Government requirements, if any
4.2.2 Class 2—Partsareheattreatedafterplatingtoincrease (see S1.7).
hardness. The coating is heat treated at 365 °C to 385 °C for
6. Materials and Manufacture
90 min (see 7.2.4).
4.2.3 Class 3—Parts are heat treated after plating at 175 °C 6.1 Pretreatment—Parts can be processed in accordance
to 205 °C for 2 h to 23 h to improve coating adhesion on steel
with Practice B656.
and for hydrogen embrittlement relief of steels (see 7.2.4). 6.1.1 A suitable method should be used to remove surface
4.2.4 Class 4—Parts are heat treated after plating at 120 °C
oxides and foreign materials which can cause poor adhesion
to 130 °C for a minimum of1hto improve adhesion on and increased porosity.
heat-treatable (age-hardened) aluminum alloys or carburized
6.1.2 A suitable method should be used to condition and
steels (see 7.2.4). activate the surface so that an adherent coating will be
4.2.5 Class 5—Parts are heat treated after plating at 365 °C
produced.
to 375 °C for a minimum of4hto improve adhesion on
6.2 Basis Material and Workmanship—Nickel boron coat-
titanium or titanium alloys (see 7.2.4).
ings will replicate the surface finish of the basis material.
4.3 The classification by grade establishes the minimum
Imperfections in the surface of the basis material including
thickness of the coating:
scratches, porosity, pits, inclusions, roll and die marks, lap
4.3.1 Grade A—Parts are plated to a minimum coating
crack, burrs, cold shuts, and surface roughness that could
thickness of 0.5 µm. adversely affect the coating should be brought to the attention
4.3.2 Grade B—Parts are plated to a minimum coating
of the purchaser prior to processing (see 7.2.1).
thickness of 12 µm.
6.3 Stress Relief—Surface-hardened parts can require stress
4.3.3 Grade C—Parts are plated to a minimum coating
reliefbeforeplating.Thestressreliefheattreatmentcanreduce
thickness of 25 µm.
the hardness of some alloys and should therefore be reviewed
4.3.4 Grade D—Parts are plated to a minimum coating
by all parties before processing (see 7.2.4). Shorter times and
thickness of 75 µm.
higher temperature can be used if the resulting loss of surface
hardness is acceptable to the purchaser.
5. Ordering Information
6.4 Hydrogen Embrittlement Relief—Hydrogen embrittle-
5.1 The purchaser should be aware of several processing
mentofhighstrengthsteelscanbeinitiatedbyseveraldifferent
considerations or options available to the processor and when
processing operations. Exposure of the parts to hydrogen
ordering should supply the information described in 5.1.1
sources will generally induce the condition. Care must be
through 5.1.15 in the purchase order and drawings.
exercised whenever high strength steel is processed to ensure
5.1.1 Title,ASTM designation number, and year of issue of
minimal exposure and timely relief treatment.
this specification.
6.5 Stress-Corrosion Cracking—Titanium and titanium al-
5.1.2 Composition and metallurgical condition of the basis
loys are subject to stress-corrosion cracking (for example, hot
metal, assemblies of dissimilar materials must be identified.
halidestress-corrosioncracking)afterprocessing.Pretreatment
5.1.3 Classification of the coating: type, class, and grade for
solutions including rinses should not contain methanol, halo-
this specification (see Section 4).
genated hydrocarbon, or more than 50 ppm chlorides, all of
5.1.4 Minimum thickness required on the significant
whichcancausesubsequentstress-corrosioncrackingwhenthe
surface, and any maximum dimensions or tolerance
parts are heated to 260 °C or higher.
requirements, if any (see 7.2.2).
5.1.5 Method of adhesion testing fromTest Method B571 to
7. Requirements
be used in acceptance requirements (see 8.3).
7.1 Process—The nickel boron coatings shall be produced
5.1.6 Requirements for certification and test reports (see
by autocatalytic nickel deposition from aqueous solutions.
Section 11).
5.1.7 Requirements for heat treatment of the part(s) for
7.2 Acceptance Requirements—The acceptance require-
stress relief prior to plating (see 6.3, 6.4, and 7.2.4). ments in 7.2.1 through 7.2.4 are required for all lots of part(s).
5.1.8 Optionalsamplingplanforlotinspectionofthepart(s)
Each lot of part(s) shall be sampled with the recommended
(see 9.1 and S1.7.1). procedure described in Section 9 of this specification.
5.1.9 Increased sampling frequency, if any, for qualification
7.2.1 Appearance—The coating shall have a uniform ap-
tests (see 7.3). pearance without visible imperfections such as blisters, pits,
5.1.10 Supplemental requirements for shot peening of the
pimples, and cracks.
part(s) (see S1.1). 7.2.1.1 Imperfections that arise from the surface condition
5.1.11 Supplementalrequirementsforweartesting(seeS1.2
of the basis metal and that cannot be removed using conven-
and S1.3). tional metal finishing techniques and that persist in the coating
5.1.12 Supplemental requirements for heat treatment in shall not be cause for rejection.
vacuum, or inert or reducing atmosphere (see 7.2.1 and S1.4). 7.2.1.2 Discoloration caused by heat treatment shall not be
5.1.13 Supplemental contact resistance requirements (see cause for rejection unless specified in the ordering information
S1.5). (see S1.4).
B607−21
8.2 g⁄cm (see Appendix X1).
7.2.2 Thickness—The coating thickness shall be measured
and conform to the specified grade (see 4.3).
8.2.1.1 Example:
7.2.3 Adhesion—The coating shall pass the adhesion test of
10 3 W
Test Method B571 as specified in the ordering information.
Thickness, µm 5 (1)
A 3 D
7.2.4 Heat Treatment:
7.2.4.1 All steel part(s) with a tensile strength of 1000 MPa
where:
or greater shall be heat treated at 190 °C 6 15 °C for stress
W = mass gain, mg,
relief in accordance with Table 1 before plating and baked
A = area of plating, cm , and
within 3 h after plating for hydrogen embrittlement relief. Heat
D = density of deposit, g/cm .
treatment for stress relief of surface hardened steels prior to
8.2.2 Metallographic Sectioning—Plate a specimen of simi-
plating shall be 140 °C 6 10 °C for 5 h.
larcompositionandmetallurgicalconditiontothepart(s)being
7.2.4.2 Class 2 coated part(s) shall be heat treated after
plated, or use a sample from the lot, cross-section, mount, and
plating in accordance with Table 1 for precipitation hardening
polish. Using a calibrated Vernier microscope, examine the
of the nickel boron deposit.
thickness of the deposit and average over 10 readings using
7.2.4.3 Heat treatment for Class 3 coated steel part(s) shall
Test Method B487.
be in accordance with Table 1.
7.2.4.4 Heat treatment for Class 4 and 5 coated part(s) other
NOTE 3—Microscopic metallographic sectioning is dependent on the
than steel basis material shall be in accordance with Table 1.
sample preparation.
7.3 Qualification Requirements—Coating and process attri-
8.2.3 Micrometer Method—Measure the part(s) or test a
butes that require testing on a monthly basis, or more fre-
coupon in a specific area before and after plating using a
quently when specified in the ordering information by the
suitable micrometer. Ensure that the specimen is at the same
purchaser. A test specimen or part, processed in a manner that
temperature for each measurem
...

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: B607 − 15 B607 − 21
Standard Specification for
Autocatalytic Nickel Boron Coatings for Engineering Use
This standard is issued under the fixed designation B607; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 Nickel boron coatings are produced by autocatalytic (electroless) deposition from aqueous solutions. These solutions contain
either an alkylamineborane or sodium borohydride as a reducing agent, a source of nickel ions, a buffer, complexant, and control
chemicals.
1.1 This specification describes the requirements for coatings of autocatalytic nickel boron deposited from aqueous solutions onto
substrates for engineering (functional) use. The specification classifies these coatings into two types:
1.1.1 Type 1 coatingsCoatings have a boron content of 0.1 to less than 3.5 mass percent with the balance nickel.
1.1.2 Type 2 coatingsCoatings have a boron content of 3.5 to 6 mass percent and a minimum of 90 mass percent nickel.
1.2 Nickel boron coatings are produced by autocatalytic (electroless) deposition from aqueous solutions. These solutions contain
either an alkylamineborane or sodium borohydride as a reducing agent, a source of nickel ions, a buffer, complexant, and control
chemicals.
1.3 The coatings are hard and uniform in thickness, even on irregular shaped parts, and used in a wide range of applications.
1.4 Process solutions formulated with an alkylamineborane usually produce coatings that contain 0.1 to 3.5 % boron. Thin
coatings of this type provide bondability and solderability on electronic components such as lead frames, electrical contacts, and
headers. To maintain solderability, these coatings are generally not heat treated.
1.5 Process solutions formulated with sodium borohydride are strongly alkaline and are frequently used to plate steel and titanium
parts to impart surface hardness and wear resistance properties. Deposits produced from these processes can contain 3 to 5 % boron
and thallium or other metals which are used to stabilize the plating solution and modify the coating properties.
1.6 The physical and mechanical properties of these deposits such as density, hardness, stress, and melting point will vary with
the boron content. The variation of boron content also affects the quantity and structure of nickel boride precipitated during heat
treatment. In the as-plated condition, the deposit consists of a predominantly amorphous mixture of nickel and boron with a
hardness of about 700 HKN. When the deposit is heated above 300°C300 °C, the nickel crystallizes, forming nickel clusters of
Ni (111) and boron precipitates as nickel boride, Ni B (211) and (311), increasing the hardness to greater than 1000 HK for Type
3 100
2 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.
Current edition approved Nov. 1, 2015Oct. 1, 2021. Published November 2015October 2021. Originally approved in 1991. Last previous edition approved in 20142015
as B607 – 91 (2014).B607 – 15. DOI: 10.1520/B0607-15.10.1520/B0607-21.
*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
B607 − 21
1.7 The nickel boron coatings are microporous and offer limited corrosion protection. Their columnar structure, however, is
beneficial in reducing wear because it provides a means of trapping lubricants within the surface of the coated part.
1.8 This document describes only autocatalytic nickel boron coatings that have been produced without use of external electric
sources.
1.9 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
1.10 The following hazards caveat pertains only to the Test Methods section of this specification: This standard does not purport
to address the safety problems 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.
NOTE 1—The following AMS standards are not requirements. They are referenced for information only: AMS 2399 and AMS 2433.
1.11 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:
B374 Terminology Relating to Electroplating
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B571 Practice for Qualitative Adhesion Testing of Metallic Coatings
B578 Test Method for Microindentation Hardness of Electroplated Coatings
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B656 Guide for Autocatalytic (Electroless) Nickel-Phosphorus Deposition on Metals for Engineering Use (Discontinued 2000)
(Withdrawn 2000)
B667 Practice for Construction and Use of a Probe for Measuring Electrical Contact Resistance
B678 Test Method for Solderability of Metallic-Coated Products
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
D2670 Test Method for Measuring Wear Properties of Fluid Lubricants (Falex Pin and Vee Block Method)
D2714 Test Method for Calibration and Operation of the Falex Block-on-Ring Friction and Wear Testing Machine
D4060 Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser
E39 Methods for Chemical Analysis of Nickel (Withdrawn 1995)
F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
2.2 Aerospace Materials Specifications:
AMS 2399 Electroless Nickel-Boron Plating
AMS 2430 Shot Peening
AMS 2433 ElectrolessPlating, Nickel-Thallium-Boron Platingor Nickel-Boron Electroless Deposition
NOTE 1—AMS 2399 and AMS 2433 are not requirements, they are referenced for information only.
2.3 U.S. Government Standards:ANSI Standard:
MIL-STD-105ANSI/ASQ Z1.4 Sampling Procedures and Tables for Inspection by Attributes
MIL-STD-13165 Shot Peening of Metal Parts
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.
The last approved version of this historical standard is referenced on www.astm.org.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
The original reference MIL-S-13165, Shot Peening of Metal Parts was cancelled in February 1998 and referred to SAE AMS-S-13165, which was also cancelled and
superseded by AMS 2430.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
The original reference MIL-STD-105 Sampling Procedures and Tables for Inspection by Attributes was cancelled in February 2008 and referred to MIL- STD-1916 or
ANSI/ASQ Z1.4.
B607 − 21
2.4 U.S. Government Standard:
MIL-STD-1916 DOD Preferred Methods for Acceptance of Product
3. Terminology
3.1 Definitions: Many terms used in this specificationare specification are defined in Terminology B374.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 cold shut—shut, n—a void on the surface which has been closed by machining and then partially opened through cleaning.
3.2.2 hot halide stress-corrosion cracking—cracking, n—a type of mechanical failure produced by halogenated solvents that have
been absorbed onto titanium and then in the presence of heat cause microcracking, and the loss of mechanical strength.
3.2.3 lap cracks—cracks, n—a surface imperfection caused by cold working of steels producing a void which can be duplicated
in the deposit.
3.2.4 significant surface—surface, n—those substrate surfaces which the coating must protect from corrosion or wear, or both, and
that are essential to the appearance.
4. Classification
4.1 The classification by type of these coatings establishes the amount of boron in the alloy.
4.1.1 Type 1—Coatings shall contain 0.1 to less than 3.5 mass percent boron with the balance nickel.
4.1.2 Type 2—Coatings shall contain 3.5 to 6 mass percent boron and a minimum of 90 mass percent nickel.
4.2 The classification by class of these coatings establishes the post treatment to be performed on the part(s). The post treatment
steps are designed to reduce the potential for hydrogen embrittlement, increase the adhesion of the coating to the substrate, improve
the fatigue properties of the part(s), and increase the wear resistance and hardness of the coating:
TABLE 1 Heat Treatment for Stress Relief Before Plating and for Hydrogen Embrittlement Relief After Plating
NOTE 1—Heat treatment for stress relief of surface hardened steels prior to plating shall be 140 ± 10°C for 5 h.
Heat treatment, minimum,
Tensile strength steel, MPa
at 190 ± 15°C, h
1000 to 1450 2
1450 to 1800 18
over 1800 23
TABLE 2 Heat Hardening of Nickel Boron Deposits
Temperature, °C Time, min
375 ± 10 90
TABLE 3 Post Heat Treatment for Class 4 and 5 Coatings
Class Temperature, °C Time, minimum, h
Class 4 125 ± 5 1
Class 5 370 ± 5 4
TABLE 1 Classification of Heat Treatment
Class Description Tensile strength steel, MPa Temperature (°C) Time (h), minimum
1 No Heat Treatment, As Plated
2 Increase Hardness 375 ± 10 1.5
3 Adhesion, Steel; Hydrogen 1000 to 1450 190 ± 15 2
Embrittlement Relief
1450 to 1800 190 ± 15 18
Over 1800 190 ± 15 23
4 Adhesion, Carburized Steel and Age 125 ± 5 1
Hardened Aluminum
5 Adhesion, Titanium or Titanium Alloys 370 ± 5 4
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
B607 − 21
4.2.1 Class 1—Parts are supplied as plated with no post heat treatment.
4.2.2 Class 2—Parts are heat treated after plating to increase hardness. The coating is heat treated at 365365 °C to 385°C385 °C
for 90 min 90 min (see 7.2.4).
4.2.3 Class 3—Parts are heat treated after plating at 180175 °C to 200°C205 °C for 22 h to 23 h to improve coating adhesion on
steel and for hydrogen embrittlement relief of steels (see 7.2.4).
4.2.4 Class 4—Parts are heat treated after plating at 120120 °C to 130°C130 °C for a minimum of 1 h to improve adhesion on
heat-treatable (age-hardened) aluminum alloys andor carburized steels (see 7.2.4).
4.2.5 Class 5—Parts are heat treated after plating at 365365 °C to 375°C375 °C for a minimum of 4 h to improve adhesion on
titanium andor titanium alloys (see 7.2.4).
4.3 The classification by grade establishes the minimum thickness of the coating:
4.3.1 Grade A—Parts are plated to a minimum coating thickness of 0.5 μm.
4.3.2 Grade B—Parts are plated to a minimum coating thickness of 12 μm.
4.3.3 Grade C—Parts are plated to a minimum coating thickness of 25 μm.
4.3.4 Grade D—Parts are plated to a minimum coating thickness of 75 μm.
5. Ordering Information
5.1 The purchaser should be aware of several processing considerations or options available to the processor and when ordering
should supply the information described in 5.1.1 through 5.1.15 in the purchase order and drawings.
5.1.1 Title, ASTM designation, designation number, and year of issue of this specification.
5.1.2 Composition and metallurgical condition of the basis metal, assemblies of dissimilar materials must be identified.
5.1.3 Classification of the coating: type, class, and grade for this specification (see Section 4).
5.1.4 Minimum thickness required on the significant surface, and any maximum dimensions or tolerance requirements, if any (see
7.2.2).
5.1.5 Method of adhesion testing from Test Method B571 to be used in acceptance requirements (see 8.3).
5.1.6 Requirements for certification and test reports (see Section 11).
5.1.7 Requirements for heat treatment of the part(s) for stress relief prior to plating (see 6.3, 6.4, and 7.2.4).
5.1.8 Optional sampling plan for lot inspection of the part(s) (see 9.1 and 13.1).S1.7.1).
5.1.9 Increased sampling frequency, if any, for qualification tests (see 7.3).
5.1.10 Supplemental requirements for shot peening of the part(s) (see 12.1).S1.1).
5.1.11 Supplemental requirements for wear testing (see 12.2S1.2 and 12.3).S1.3).
5.1.12 Supplemental requirements for heat treatment in vacuum, or inert or reducing atmosphere (see 7.2.1 &and 12.4).S1.4).
5.1.13 Supplemental contact resistance requirements (see 12.5).S1.5).
5.1.14 Supplemental solderability requirements (see 12.6).S1.6).
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5.1.15 Supplemental U.S. Government requirements, if any (see Section S1.7).13).
6. Materials and Manufacture
6.1 Pretreatment—Parts can be processed in accordance with Practice B656.
6.1.1 A suitable method should be used to remove surface oxides and foreign materials which can cause poor adhesion and
increased porosity.
6.1.2 A suitable method should be used to condition and activate the surface so that an adherent coating will be produced.
6.2 Basis Material and Workmanship—Nickel boron coatings will replicate the surface finish of the basis material. Imperfections
in the surface of the basis material including scratches, porosity, pits, inclusions, roll and die marks, lap crack, burrs, cold shuts,
and surface roughness that could adversely affect the coating should be brought to the attention of the purchaser prior to processing
(see 7.2.1).
6.3 Stress Relief—Surface-hardened parts can require stress relief before plating. The stress relief heat treatment can reduce the
hardness of some alloys and should therefore be reviewed by all parties before processing (see 5.1.7 and 7.2.4). Shorter times and
higher temperature can be used if the resulting loss of surface hardness is acceptable to the purchaser.
6.4 Hydrogen Embrittlement Relief—Hydrogen embrittlement of high strength steels can be initiated by several different
processing operations. Exposure of the parts to hydrogen sources will generally induce the condition. Care must be exercised
whenever high strength steel is processed to ensure minimal exposure and timely relief treatment.
6.5 Stress-Corrosion Cracking—Titanium and titanium alloys are subject to stress-corrosion cracking (for example, hot halide
stress-corrosion cracking) after processing. Pretreatment solutions including rinses should not contain methanol, halogenated
hydrocarbon, or more than 50 ppm chlorides, all of which can cause subsequent stress-corrosion cracking when the parts are heated
to 260°C260 °C or higher.
7. Requirements
7.1 Process—The nickel boron coatings shall be produced by autocatalytic nickel deposition from aqueous solutions.
7.2 Acceptance Requirements—The acceptance requirements in 7.2.1 through 7.2.4 are required for all lots of part(s). Each lot of
part(s) shall be sampled with the recommended procedure described in Section 9 of this specification.
7.2.1 Appearance—The coating shall have a uniform appearance without visible imperfections such as blisters, pits, pimples, and
cracks.
7.2.1.1 Imperfections that arise from the surface condition of the basis metal and that cannot be removed using conventional metal
finishing techniques and that persist in the coating shall not be cause for rejection.
7.2.1.2 Discoloration caused by heat treatment shall not be cause for rejection unless specified in the ordering information (see
5.1.12 and S1.4).12.4).
7.2.2 Thickness—The coating thickness shall be measured and conform to the specified grade.grade (see 4.3).
7.2.3 Adhesion—The coating shall pass the adhesion test of Test Method B571 as specified in the ordering information (see
information.5.1.15).
7.2.4 Heat Treatment:
7.2.4.1 All steel part(s) with a tensile strength of 1000 MPa or greater shall be heat treated at 190190 °C 6 15°C15 °C for stress
relief in accordance with Table 1 before plating and baked within 3 h 3 h after plating for hydrogen embrittlement relief. Heat
treatment for stress relief of surface hardened steels prior to plating shall be 140 °C 6 10 °C for 5 h.
B607 − 21
7.2.4.2 Class 2 coated part(s) shall be heat treated after plating in accordance with Table 21 for precipitation hardening of the
nickel boron deposit.
7.2.4.3 Heat treatment for Class 3 coated steel part(s) shall be in accordance with Table 1.
7.2.4.4 Heat treatment for Class 4 and 5 coated part(s) other than steel basis material shall be in accordance with Table 31.
7.3 Qualification Requirements—Coating and process attributes that require testing on a monthly basis, or more frequently when
specified in the ordering information by the purchaser. A test specimen or part, processed in a manner that duplicates the
characteristics of production parts, shall be produced and used in these tests.
7.3.1 Hardness—The hardness of the Type 2, Class 2, Grade C and D coating shall be not less than 1000 HK as measured by
Test Method B578.
7.3.2 Composition—The coating composition produced from the process shall be analyzed for nickel and boron. The alloy
produced shall be within the range specified for the coating type.
7.3.3 Hydrogen Embrittlement—The process and coating used to deposit a coating onto high strength steels shall be evaluated for
freedom from hydrogen embrittlement and pass requirements of by Test Method F519.
8. Test Methods
8.1 Test Specimens:
8.1.1 When separate test specimens are required, the number to be used, the material from which they are to be made, and their
shape and size shall be specified by the purchaser.
8.1.2 When separate test specimens are used for acceptance or qualification testing of the coating, the specimens shall be made
of the same material as the part(s), have the same metallurgical condition as the part(s), and be processed with the part(s).
8.2 Thickness—The thickness shall be measured at any place on the significant surface designated by the purchaser, and the
measurement shall be made with an accuracy of better than 10 % by a m
...