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How to increase hardness of the electroformed sheets of nickel

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I am in hologram bussiness. I have nickel sulfamate bath to produce electroformed thin nickel sheets. I want to increase the hardness of the sheets. Any suggestions? For me the most preferable method would be playing with existing process parameters (if possible!) rather than using additives...
Moreover, I appreciate if someone gives advice about the operation of the hull cell equipment. By carrying out hull cell tests, which information can I get about how the bath contents (concentrations) effect the produced sheet, and the current density, throwing power etc....... Thank you for your replies allready! :)

Onur Keyes
plating shop - UK

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Moving to nickel-cobalt is probably the best way to improve the properties, including hardness.

Ted Mooney, P.E. finishing.com Brick, New Jersey

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First of three simultaneous responses -- +++++

Ted's idea will work, but it requires quite a bit more frequent lab testing until cobalt additions are down to an amp/hour science.
Another common hardener is sodium tungstanate. Requires tougher testing than cobalt and normally costs more, but can go slightly harder.

James Watts
- Navarre, Florida

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Second of three simultaneous responses -- +++++

Nickel can be given increased hardnesses by either adding up to 1g/l sodium saccharin or by using nickel-cobalt alloys. The former is susceptible to sulphur embrittlement if used at temperatures above about 160C and the latter is more difficult to control.

Trevor Crichton R&D practical scientist The Pheasantries - Chesham, U.K.

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Third of three simultaneous responses -- +++++

Just to add that the tensiometer, rather than the Hull cell, is the tool of choice for electroformers. Hope you already have one and use it.

Guillermo Marrufo
Monterrey, NL, Mexico