ASTM B733-97
(Specification)Standard Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal
Standard Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal
SCOPE
1.1 This specification covers requirements for autocatalytic (electroless) nickel-phosphorus coatings applied from aqueous solutions to metallic products for engineering (functional) uses.
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Designation: B 733 – 97
Standard Specification for
Autocatalytic (Electroless) Nickel-Phosphorus Coatings on
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Metal
This standard is issued under the fixed designation B 733; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 1.8 The medium phosphorous coatings (5 to 9 % P) are most
widely used to meet the general purpose requirements of wear
1.1 This specification covers requirements for autocatalytic
and corrosion resistance.
(electroless) nickel-phosphorus coatings applied from aqueous
1.9 The high phosphorous (more than 10 % P) coatings
solutions to metallic products for engineering (functional) uses.
have superior salt-spray and acid resistance in a wide range of
1.2 The coatings are alloys of nickel and phosphorus pro-
applications. They are used on beryllium and titanium parts for
duced by autocatalytic chemical reduction with hypophosphite.
low stress properties. Coatings with phosphorus contents
Because the deposited nickel alloy is a catalyst for the reaction,
greater than 11.2 % P are not considered to be ferromagnetic.
the process is self-sustaining. The chemical and physical
1.10 The values stated in SI units are to be regarded as
properties of the deposit vary primarily with its phosphorus
standard.
content and subsequent heat treatment. The chemical makeup
1.11 The following precautionary statement pertains only to
of the plating solution and the use of the solution can affect the
the test method portion, Section 9, of this specification. This
porosity and corrosion resistance of the deposit. For more
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standard does not purport to address all of the safety concerns,
details, see ASTM STP 265 (1) and Refs (2) (3) (4) and (5)
if any, associated with its use. It is the responsibility of the user
also refer to Figs. X1.1, Figs. X1.2, and Figs. X1.3 in the
of this standard to establish appropriate safety and health
Appendix of Guide B 656.
practices and determine the applicability of regulatory limita-
1.3 The coatings are generally deposited from acidic solu-
tions prior to use.
tions operating at elevated temperatures.
1.4 The process produces coatings of uniform thickness on
2. Referenced Documents
irregularly shaped parts, provided the plating solution circu-
2.1 ASTM Standards:
lates freely over their surfaces.
B 368 Test Method for Copper-Accelerated Acetic Acid-
1.5 The coatings have multifunctional properties, such as
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Salt Spray (Fog) Testing (CASS Testing)
hardness, heat hardenability, abrasion, wear and corrosion
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B 374 Terminology Relating to Electroplating
resistance, magnetics, electrical conductivity provide diffusion
B 380 Test Method of Corrosion by the Corrodkote Proce-
barrier, and solderability. They are also used for the salvage of
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dure
worn or mismachined parts.
B 487 Test Method for Measurement of Metal and Oxide
1.6 The low phosphorus (2 to 4 % P) coatings are microc-
Coating Thicknesses by Microscopical Examination of a
rystalline and possess high as-plated hardness (620 to 750 HK
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Cross Section
100). These coatings are used in applications requiring abra-
B 499 Test Method for Measurement of Coating Thick-
sion and wear resistance.
nesses by the Magnetic Method: Nonmagnetic Coatings on
1.7 Lower phosphorus deposits in the range between 1 and
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Magnetic Basis Metals
3 % phosphorus are also microcrystalline. These coatings are
B 504 Test Method for Measurement of Thickness of Me-
used in electronic applications providing solderability, bond-
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tallic Coatings by the Coulometric Method
ability, increased electrical conductivity, and resistance to
B 537 Practice for Rating of Electroplated Panels Subjected
strong alkali solutions.
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to Atmospheric Exposure
B 567 Method for Measurement of Coating Thickness by
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the Beta Backscatter Method
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This specification is under the jurisdiction of ASTM Committee B-08 on Metal
B 568 Method for Measurement of Coating Thickness by
Powders and Metal Powder Products and is the direct responsibility of Subcom-
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X-Ray Spectrometry
mittee B08.08.01 on Engineering Coatings.
Current edition approved July 10, 1997. Published October 1997. Originally
published as B 733 – 84. Last previous edition B 733 – 90 (1994).
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The boldface numbers given in parentheses refer to a list of references at the
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end of the text. Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B733–97
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