Letter 41006

Nickel electroforming coating hardness [India] 

June 5, 2006

We are not getting hardness less than 150 on vicker scale.What is the required condition of the sulphamate bath.
I have worked with the following bath condition
cd 3.5A
temp 50degree C
air agitation
cathode movement
S Nickel anode

M.K Rao
Forging - Mysore, Karnataka, India

You probably have unwanted drag in material or breakdown products or an excess of SNAP A/M (or equivalent). I would do a good carbon treatment, check the bath for all parameters and try again. Should work if your pH is 4.0 + or - 0.1

James Watts
- FL

You didn't mention the pH but anyway a sulfamate bath does not give you much chance to move it or raise the temp. Perhaps reducing you current to 1-2.5 A/dm2. Also important is to control impurities specially hexchrome, sulfate and ammonia. Check your hardness indenter shape and force, it might be misleading you.

Guillermo Marrufo
Monterrey, NL, Mexico

Dear Mr. Rao,
What is the hardness required in nickel Electroforming?
To get minimum hardness avoid chloride in sulphamate bath . S nickel will dissolutes to 1-3 gms of Nickel chloride. Also at less cd and low temperature without any additive addition you can get the low hardness. controlling chloride in the bath is very important.

Ramesh Modi
- Maharashtra

I would not expect to get any nickel hardness less than 150Hv, so I reckon the bath is doing what is is designed to do. What hardness do you want?

Trevor Crichton R&D practical scientist - UK

W.H. Safranek's book The Properties of Electrodeposited Metals and Alloys gives a range of 140 to 650hV. Another more generic reference says 250 to 300.
Lead and iron impurities raise the hardness. Try holding your pH to a tight range of 3.8 to 4.0.

James Watts
- FL

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