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Determination of the Porosity of Precious Metal Platings using Chronocoulometry

IP.com Disclosure Number: IPCOM000040990D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Henning, TP: AUTHOR

Abstract

A quantitative determination of the porosity of various precious metal platings is accomplished by a test method that utilizes chronocoulometry. The test is described in the following.

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Determination of the Porosity of Precious Metal Platings using Chronocoulometry

A quantitative determination of the porosity of various precious metal platings is accomplished by a test method that utilizes chronocoulometry. The test is described in the following.

A sample to be tested is placed in a solution of water and a supporting electrolyte. A reference electrode and a counter electrode are placed in the solution. Using a potentiostat, the potential of the sample is stepped down from a potential at which the oxidation of Ni does not occur to a potential at which the oxidation does occur. The current that flows between the sample and the counter electrode is integrated for the length of time of the oxidation step. The integrated charge of coulombs is proportional to the exposed area of Ni in the plated deposit. By refering to a calibration chart made by performing the same test on plated samples of known exposed areas, a quantitative evaluation of the exposed Ni can be made.

The described test method can be illustrated in the following example.

Flat coupons of brass are plated with 100 microinches of Ni. A small section of the Ni plated coupon is masked, 1.0% of the area, then plated with a thick, soft Au plate ( 200 microinches). The thick Au plating is assumed to be nonporous. The masked area is stripped leaving 1.0% of the area as exposed Ni. A similar sample is plated without the exposed Ni. The test method is then used on the samples with the following...