ASTM B984 - 12
Standard Specification for Electrodeposited Coatings of Palladium- Cobalt Alloy for Engineering Use
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Abstract
This specification covers requirements for electrodeposited palladium-cobalt alloy coatings containing approximately 80% of palladium and 20% of cobalt. It also covers composite coatings consisting of palladium-cobalt with a thin gold overplate for applications involving electrical contacts. Palladium and palladium-cobalt remain competitive finishes for high reliability applications. The specification deals with material classification, ordering information, materials and manufacture, coating requirements, sampling, test methods, special government requirements, and other requirements.
This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.
1. Scope
1.1 This specification covers requirements for electrodeposited palladium-cobalt alloy coatings containing approximately 80% of palladium and 20% of cobalt. Composite coatings consisting of palladium-cobalt with a thin gold overplate for applications involving electrical contacts are also covered. Palladium and palladium-cobalt remain competitive finishes for high reliability applications.
1.2 Properties—Palladium is the lightest and least noble of the platinum group metals (1)2. IIt has the density of 12 gm per cubic centimeter, specific gravity of 12.0, that is substantially lower than the density of gold, 19.29 gm per cubic centimeter, specific gravity 19.3, and platinum 21.48 gm per cubic centimeter, specific gravity 21.5. The density of cobalt on the other hand is even less than palladium. It is only 8.69 gm per cubic centimeter, specific gravity 8.7. This yields a greater volume or thickness of coating and, consequently, some saving of metal weight and reduced cost. Palladium-cobalt coated surface provides a hard surface finish (ASTM E18) thus decreasing wear and increasing durability. Palladium-cobalt coated surface also has very low coefficient of friction 0.43 compared to hard gold 0.60 thus providing lower mating and unmating forces for electrical contacts (1) 2. Palladium-cobalt has smaller grain size (ASTM E112), 50 – 150 Angstroms, compared to Hard Gold 200 – 250 Angstroms (1)2. 5 – 15 nanometer, compared to hard gold 20 – 25 nanometer (1)2. Palladium-cobalt has low porosity (ASTM B799) 0.2 porosity index compared to hard gold 3.7 porosity index (1)2. Palladium-cobalt coated surface has higher ductility (ASTM B489) 3-7 than that of hard gold <3 (1)2. The palladium-cobalt coated surface is also thermally more stable 395°C than hard gold 150°C, and silver 170°C. The following Table 1 compares the hardness range of electrodeposited palladium-cobalt with other electrodeposited noble metals and alloys (3,4).2
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| Approximate Hardness (HK25) |
| Gold | 50–250 |
| Palladium | 75–600 |
| Platinum | 150–550 |
| Palladium-Nickel | 300–650 |
| Palladium-Cobalt | 500–650 |
| Rhodium | 750–1100 |
| Ruthenium | 600–1300 |
1.3 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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. Some specific hazards statements are given in Section 7 on Hazards.
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
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
B281 Practice for Preparation of Copper and Copper-Base Alloys for Electroplating and Conversion Coatings
B322 Guide for Cleaning Metals Prior to Electroplating
B343 Practice for Preparation of Nickel for Electroplating with Nickel
B374 Terminology Relating to Electroplating
B481 Practice for Preparation of Titanium and Titanium Alloys for Electroplating
B482 Practice for Preparation of Tungsten and Tungsten Alloys for Electroplating
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B488 Specification for Electrodeposited Coatings of Gold for Engineering Uses
B489 Practice for Bend Test for Ductility of Electrodeposited and Autocatalytically Deposited Metal Coatings on Metals
B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals
B507 Practice for Design of Articles to Be Electroplated on Racks
B542 Terminology Relating to Electrical Contacts and Their Use
B558 Practice for Preparation of Nickel Alloys for Electroplating
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
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B679 Specification for Electrodeposited Coatings of Palladium for Engineering Use
B689 Specification for Electroplated Engineering Nickel Coatings
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B741 Test Method for Porosity In Gold Coatings On Metal Substrates By Paper Electrography
B748 Test Method for Measurement of Thickness of Metallic Coatings by Measurement of Cross Section with a Scanning Electron Microscope
B762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
B765 Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
B799 Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
B809 Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (Flowers-of-Sulfur)
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
D3951 Practice for Commercial Packaging
E18 Test Methods for Rockwell Hardness of Metallic Materials
E112 Test Methods for Determining Average Grain Size
ICS Code
ICS Number Code 25.220.40 (Metallic coatings)
UNSPSC Code
UNSPSC Code
Referencing This Standard
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DOI: 10.1520/B0984-12
Citation Format
ASTM B984-12, Standard Specification for Electrodeposited Coatings of Palladium- Cobalt Alloy for Engineering Use, ASTM International, West Conshohocken, PA, 2012, www.astm.org
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