ASTM B799-95(2014)
Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor

Standard No.

ASTM B799-95(2014)

Release Date

1995

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM B799-95(2020)

Latest

ASTM B799-95(2020)

Scope

5.1 Gold coatings are often specified for the contacts of separable electrical connectors and other devices. Electrodeposits are the form of gold that is most used on contacts, although it is also employed as inlay or clad metal and as weldments on the contact surface. The intrinsic nobility of gold enables it to resist the formation of insulating oxide films that could interfere with reliable contact operation.

5.2 Palladium coatings are sometimes specified as alternatives to gold on electrical contacts and similar electrical component surfaces, both as electrodeposits and as inlay or clad metal. This test method is particularly suitable for determining porosity in palladium coatings, since the reactive atmosphere that is used does not attack the palladium if the specified test conditions are followed. In contrast, palladium coatings are attacked by nitric acid (HNO₃) and other strong oxidizing agents, so that Test Method B735 cannot be used for determining the porosity in such coatings.

5.3 In order for these coatings to function as intended, porosity, cracks, and other defects in the coating that expose base-metal substrates and underplates must be minimal or absent, except in those cases where it is feasible to use the contacts in structures that shield the surface from the environment or where corrosion inhibiting surface treatments for the deposit are employed. The level of porosity in the coating that may be tolerable depends on the severity of the environment to the underplate or substrate, design factors for the contact device like the force with which it is mated, circuit parameters, and the reliability of contact operation that it is necessary to maintain. Also, when present, the location of pores on the surface is important. If the pores are few in number and are outside of the zone of contact of the mating surfaces, their presence can often be tolerated.

5.4 Methods for determining pores on a contact surface are most suitable if they enable their precise location and numbers to be determined. Contact surfaces are often curved or irregular in shape, and testing methods should be suitable for them. In addition, the severity of porosity-determining tests may vary from procedures capable of detecting all porosity to procedures that detect only highly porous conditions.

5.5 The present test method is capable of detecting virtually all porosity or other defects that could participate in corrosion reactions with the substrate or underplate. The test is rapid, simple, and inexpensive. In addition, it can be used on contacts having complex geometry such as pin-socket contacts (although with deep recesses it is preferred that the contact structures be opened to permit reaction of the sulfur dioxide with the interior significant surfaces).

5.6 The relationship of porosity levels revealed by particular tests to contact behavior must be made by the user of these tests through practical experience or by judgment. Thus, absence of porosity in the coating may be a requirement for some applications, while a few pores in the contact zone may be acceptable for others.

5.7 This test is considered destructive in that it reveals the p......

ASTM B799-95(2014) Referenced Document

• ASTM B374 Standard Terminology Relating to Electroplating*， 1996-04-20 Update
• ASTM B542 Standard Terminology Relating to Electrical Contacts and Their Use*， 2019-11-01 Update
• ASTM B735 Standard Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor
• ASTM B741 Standard Test Method for Porosity In Gold Coatings On Metal Substrates By Paper Electrography
• ASTM B765 Standard Guide for Selection of Porosity Tests for Electrodeposits and Related Metallic Coatings
• ASTM B798 Standard Test Method for Porosity in Gold or Palladium Coatings on Metal Substrates by Gel-Bulk Electrography*， 2020-04-01 Update
• ASTM B809 Standard Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor ("Flowers-of-Sulfur")*， 2024-04-20 Update

ASTM B799-95(2014) history

• 2020 ASTM B799-95(2020) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
• 1995 ASTM B799-95(2014) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
• 1995 ASTM B799-95(2009) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
• 1995 ASTM B799-95(2005) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
• 2000 ASTM B799-95(2000) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor