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Control Of pH Factor For Yielding Higher Coercivity

IP.com Disclosure Number: IPCOM000097322D
Original Publication Date: 1962-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Croll, IM: AUTHOR [+2]

Abstract

In the deposition of cobalt and cobalt nickel platings, respectively, from salt solutions of cobalt and cobalt nickel, employing unmodified D.C. current, higher coercivities are realized by maintaining the pH factor above the critical pH value characteristic of each bath solution.

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Control Of pH Factor For Yielding Higher Coercivity

In the deposition of cobalt and cobalt nickel platings, respectively, from salt solutions of cobalt and cobalt nickel, employing unmodified D.C. current, higher coercivities are realized by maintaining the pH factor above the critical pH value characteristic of each bath solution.

In unbuffered chloride and sulfate baths, the critical pH is in the region of 3.5 - 4.5. In the case of acetate baths, the critical pH occurs in the region of 5.5 - 6.5. If a buffering agent such as boric acid is used, the critical pH is in the region of 6.0 - 7.0

For nickel cobalt alloy deposits of 0. 05 mils thickness, coercivities of over 450 oersteds are obtained. In the case of cobalt deposits of the same thickness, coercivities of over 350 oersteds are obtained.

A typical, although not exclusive formulation is:

Bath composition: 1/4 MCoSO(4), 1/4 MNiCl(2)

pH: 6.0

Current density: 40 amps/ft2

Temperature: 25 degrees C.

The coercivity of these platings decreases with increasing thickness. This effect is less pronounced when the plating bath contains boric acid, in which case platings of 1 mil thickness are prepared which have coervicities of 400 oersteds. With the unbuffered baths, greater effective plating thickness is obtained without decrease in coercive force such is realized by successive deposition of thin magnetic platings separated by thin flashes of copper obtained by replacement reaction with CU/++/ ion in solution or by...