ASTM B733-04

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

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    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 STP 265 (1) and Refs (2) (3) (4)and ().

    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 , 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.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    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 Coulometric Method

    B537 Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure

    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 Microhardness of Electroplated Coatings

    B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings

    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

    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

    B851 Specification for Automated Controlled Shot Peening of Metallic Articles Prior to Nickel, Autocatalytic Nickel, or Chromium Plating, or as Final Finish

    D1193 Specification for Reagent Water

    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

    D3951 Practice for Commercial Packaging

    D4060 Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser

    E60 Practice for Analysis of Metals, Ores, and Related Materials by Spectrophotometry

    E140 Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, and Scleroscope Hardness

    E156 Test Method for Determination of Phosphorus in High-Phosphorus Brazing Alloys (Photometric Method)

    E352 Test Methods for Chemical Analysis of Tool Steels and Other Similar Medium- and High-Alloy Steels

    F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments

    G5 Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements

    G31 Guide for Laboratory Immersion Corrosion Testing of Metals

    G59 Test Method for Conducting Potentiodynamic Polarization Resistance Measurements

    G85 Practice for Modified Salt Spray (Fog) Testing

    Military Standards

    MIL-STD-105 Sampling Procedures and Tables for Inspection by Attribute

    ISO Standards

    ISO4527 Autocatalytic Nickel-Phosphorus Coatings--Specification and Test Methods Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.


    ICS Code

    ICS Number Code 25.220.40 (Metallic coatings)

    UNSPSC Code

    UNSPSC Code


    DOI: 10.1520/B0733-04

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