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Solution Addition to Prevent Corrosion of Alloys

IP.com Disclosure Number: IPCOM000083474D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Chaudhari, P: AUTHOR [+3]

Abstract

When an electrode of silver-palladium is joined by lead-tin solder, a reaction between the palladium and the lead-tin occurs which depletes palladium from the electrode, and the free silver that is left behind can be corroded. In other words, although silver-palladium alloy is itself not subject to corrosion, it is no longer so when the depletion of palladium occurs.

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Solution Addition to Prevent Corrosion of Alloys

When an electrode of silver-palladium is joined by lead-tin solder, a reaction between the palladium and the lead-tin occurs which depletes palladium from the electrode, and the free silver that is left behind can be corroded. In other words, although silver-palladium alloy is itself not subject to corrosion, it is no longer so when the depletion of palladium occurs.

A copper-nickel alloy behaves in the same manner as silver-palladium when it reacts with lead-tin solder to form a nickel-tin compound, which depletes nickel and forms free copper which can also be corroded by an appropriate atmosphere. These examples show that the phenomenon of depletion of one constituent from a binary alloy which is not subject to corrosion, can leave the remaining constituent open to corrosion attack. Corrosion resistance under such conditions can be provided by the addition of a third element.

The third element is chosen by the following criteria:
(1) The third element forms a ternary solid solution with the

base binary alloy.
(2) The third element does not react to form compounds with the

depleting agency, i.e., it does not react with the solder or

other material as mentioned hereinabove. This criterion

includes not only those elements that by themselves do not

form compounds with the depleting agency, but also those

which in the presence of the base alloy will not form

compounds with the depleting agency.

To illustrate how the present solution works, first consider silver-palladium in the lead-tin solder environment to show how corrosion takes place. When palladium is alloyed with silver to protect the silver fro...