ASTM B733-15

Standard Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal

ABSTRACT
This specification establishes the requirements for autocatalytic (electroless) nickel-phosphorus coatings applied from acidic aqueous solutions to metallic products for use in engineering functions operating at elevated temperatures. The coatings covered here are alloys of nickel and phosphorus produced by self-sustaining autocatalytic chemical reduction with hypophosphite. The coatings are grouped into the following classification systems: types, which are based on the general composition with respect to phosphorus; service condition numbers, which are based on the severity of exposure to which the coating is intended to perform and the corresponding minimum thickness that will provide satisfactory performance; and post heat treatment class, which are based on post-plating heat treatment temperature and time to produce the desired adhesion and hardness improvements. Prior to plating, substrates should be pretreated by stress relief for reducing risks of hydrogen embrittlement, peening, and racking. The coatings shall be sampled and tested accordingly to evaluate both acceptance (appearance, thickness, adhesion, and porosity) and qualification requirements (composition, microhardness, and hydrogen embrittlement). Thickness shall be assessed either by microscopical method, a magnetic induction instrument, beta backscatter method, a micrometer, weigh-plate-weigh method, coulometric method, or X-ray spectrometry. Adhesion shall be examined either by bend, impact, or thermal shock tests. And porosity shall be inspected either by ferroxyl test, boiling water test, aerated water test, or alizarin test.
SCOPE
1.1 This specification covers requirements for autocatalytic (electroless) nickel-phosphorus coatings applied from aqueous solutions to metallic products for engineering (functional) uses.  
1.2 The coatings are alloys of nickel and phosphorus produced by autocatalytic chemical reduction with hypophosphite. Because the deposited nickel alloy is a catalyst for the reaction, the process is self-sustaining. The chemical and physical properties of the deposit vary primarily with its phosphorus content and subsequent heat treatment. The chemical makeup of the plating solution and the use of the solution can affect the porosity and corrosion resistance of the deposit. For more details, see ASTM STP 265  (1)2 and Refs  (2) (3) (4) and (5).  
1.3 The coatings are generally deposited from acidic solutions operating at elevated temperatures.  
1.4 The process produces coatings of uniform thickness on irregularly shaped parts, provided the plating solution circulates freely over their surfaces.  
1.5 The coatings have multifunctional properties, such as hardness, heat hardenability, abrasion, wear and corrosion resistance, magnetics, electrical conductivity provide diffusion barrier, and solderability. They are also used for the salvage of worn or mismachined parts.  
1.6 The low phosphorus (2 to 4 % P) coatings are microcrystalline and possess high as-plated hardness (620 to 750 HK 100). These coatings are used in applications requiring abrasion and wear resistance.  
1.7 Lower phosphorus deposits in the range between 1 and 3 % phosphorus are also microcrystalline. These coatings are used in electronic applications providing solderability, bondability, increased electrical conductivity, and resistance to strong alkali solutions.  
1.8 The medium phosphorous coatings (5 to 9 % P) are most widely used to meet the general purpose requirements of wear and corrosion resistance.  
1.9 The high phosphorous (more than 10 % P) coatings have superior salt-spray and acid resistance in a wide range of applications. They are used on beryllium and titanium parts for low stress properties. Coatings with phosphorus contents greater than 11.2 % P are not considered to be ferromagnetic.  
1.10 The values stated in SI units are to be regarded as standard.  
1.11 The following precautionary statement pertains only to the t...

General Information

• Status: Historical
• Publication Date: 31-Oct-2015
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.03 - Engineering Coatings

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:B733 −15
Standard Specification for
Autocatalytic (Electroless) Nickel-Phosphorus Coatings on
1
Metal
This standard is issued under the fixed designation B733; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope bondability, increased electrical conductivity, and resistance to
strong alkali solutions.
1.1 This specification covers requirements for autocatalytic
(electroless) nickel-phosphorus coatings applied from aqueous 1.8 Themediumphosphorouscoatings(5to9%P)aremost
widely used to meet the general purpose requirements of wear
solutionstometallicproductsforengineering(functional)uses.
and corrosion resistance.
1.2 The coatings are alloys of nickel and phosphorus pro-
1.9 The high phosphorous (more than 10% P) coatings
ducedbyautocatalyticchemicalreductionwithhypophosphite.
have superior salt-spray and acid resistance in a wide range of
Becausethedepositednickelalloyisacatalystforthereaction,
applications.Theyareusedonberylliumandtitaniumpartsfor
the process is self-sustaining. The chemical and physical
low stress properties. Coatings with phosphorus contents
properties of the deposit vary primarily with its phosphorus
greater than 11.2% P are not considered to be ferromagnetic.
content and subsequent heat treatment. The chemical makeup
oftheplatingsolutionandtheuseofthesolutioncanaffectthe
1.10 The values stated in SI units are to be regarded as
porosity and corrosion resistance of the deposit. For more
standard.
2
details, see ASTM STP 265 (1) and Refs (2)(3)(4) and (5).
1.11 Thefollowingprecautionarystatementpertainsonlyto
1.3 The coatings are generally deposited from acidic solu-
the test method portion, Section 9, of this specification. This
tions operating at elevated temperatures.
standard does not purport to address all of the safety concerns,
if any, associated with its use. It is the responsibility of the user
1.4 The process produces coatings of uniform thickness on
of this standard to establish appropriate safety and health
irregularly shaped parts, provided the plating solution circu-
practices and determine the applicability of regulatory limita-
lates freely over their surfaces.
tions prior to use.
1.5 The coatings have multifunctional properties, such as
hardness, heat hardenability, abrasion, wear and corrosion
2. Referenced Documents
resistance, magnetics, electrical conductivity provide diffusion
3
2.1 ASTM Standards:
barrier, and solderability.They are also used for the salvage of
B368Test Method for Copper-AcceleratedAceticAcid-Salt
worn or mismachined parts.
Spray (Fog) Testing (CASS Test)
1.6 The low phosphorus (2 to 4% P) coatings are microc-
B374Terminology Relating to Electroplating
rystalline and possess high as-plated hardness (620 to 750 HK
B380Test Method for Corrosion Testing of Decorative
100). These coatings are used in applications requiring abra-
Electrodeposited Coatings by the Corrodkote Procedure
sion and wear resistance.
B487Test Method for Measurement of Metal and Oxide
Coating Thickness by Microscopical Examination of
1.7 Lower phosphorus deposits in the range between 1 and
Cross Section
3% phosphorus are also microcrystalline. These coatings are
B499Test Method for Measurement of CoatingThicknesses
used in electronic applications providing solderability,
by the Magnetic Method: Nonmagnetic Coatings on
Magnetic Basis Metals
B504Test Method for Measurement of Thickness of Metal-
1
This specification is under the jurisdiction of ASTM Committee B08 on
lic Coatings by the Coulometric Method
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.03 on Engineering Coatings.
Current edition approved Nov. 1, 2015. Published November 2015. Originally
3
approvedin1984.Lastpreviouseditionapprovedin2014asB733–09(2014).DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/B0733-15. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
2
The boldface numbers given in parentheses refer to a list of references at the Standards volume information, refer to the standard’s Document Summary page on
end of the text. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B733−15
B537Practice for Rating of Electroplated Panels Subjected G85Practice for Modified Salt Spray (Fog) Testing
to Atmospheric Exposure
2.2 Military Standards:
5
B567Test Method for Measurement of
...

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: B733 − 04 (Reapproved 2014) B733 − 15
Standard Specification for
Autocatalytic (Electroless) Nickel-Phosphorus Coatings on
1
Metal
This standard is issued under the fixed designation B733; 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
1.1 This specification covers requirements for autocatalytic (electroless) nickel-phosphorus coatings applied from aqueous
solutions to metallic products for engineering (functional) uses.
1.2 The coatings are alloys of nickel and phosphorus produced by autocatalytic chemical reduction with hypophosphite.
Because the deposited nickel alloy is a catalyst for the reaction, the process is self-sustaining. The chemical and physical properties
of the deposit vary primarily with its phosphorus content and subsequent heat treatment. The chemical makeup of the plating
solution and the use of the solution can affect the porosity and corrosion resistance of the deposit. For more details, see ASTM
2
STP 265 (1) and Refs (2) (3) (4) and (5).
1.3 The coatings are generally deposited from acidic solutions operating at elevated temperatures.
1.4 The process produces coatings of uniform thickness on irregularly shaped parts, provided the plating solution circulates
freely over their surfaces.
1.5 The coatings have multifunctional properties, such as hardness, heat hardenability, abrasion, wear and corrosion resistance,
magnetics, electrical conductivity provide diffusion barrier, and solderability. They are also used for the salvage of worn or
mismachined parts.
1.6 The low phosphorus (2 to 4 % P) coatings are microcrystalline and possess high as-plated hardness (620 to 750 HK 100).
These coatings are used in applications requiring abrasion and wear resistance.
1.7 Lower phosphorus deposits in the range between 1 and 3 % phosphorus are also microcrystalline. These coatings are used
in electronic applications providing solderability, bondability, increased electrical conductivity, and resistance to strong alkali
solutions.
1.8 The medium phosphorous coatings (5 to 9 % P) are most widely used to meet the general purpose requirements of wear and
corrosion resistance.
1.9 The high phosphorous (more than 10 % P) coatings have superior salt-spray and acid resistance in a wide range of
applications. They are used on beryllium and titanium parts for low stress properties. Coatings with phosphorus contents greater
than 11.2 % P are not considered to be ferromagnetic.
1.10 The values stated in SI units are to be regarded as standard.
1.11 The following precautionary statement pertains only to the test method portion, Section 9, of this specification.This
standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user
of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior
to use.
1
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, 2014Nov. 1, 2015. Published November 2014November 2015. Originally approved in 1984. Last previous edition approved in 20092014
as B733 – 09.B733 – 09(2014). DOI: 10.1520/B0733-04R14.10.1520/B0733-15.
2
The boldface numbers given in parentheses refer to a list of references at the end of the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B733 − 15
2. Referenced Documents
3
2.1 ASTM Standards:
B368 Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
B374 Terminology Relating to Electroplating
B380 Test Method for Corrosion Testing of Decorative Electrodeposited Coatings by the Corrodkote Procedure
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis
Metals
B504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometr
...