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Hardness of Nickel Plating?

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Which Nickel plating process, electro-plating or electroless will provide the harder finish when used on commercial standard mild steel sheet.

Also, does anyone have an idea of the range of hardness values for these finishes.

Neil Roberts
- Slough Berksire England


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Generally speaking, the microhardness of electroplated nickel ranges from HV 150 to 350 ,while the microhardness of electrless nickel is around HV 600, and with proper heat treatment, HV 1000 can be achieved for electroless nickel.

Ling

Ling Hao
- Grand Rapids, Michigan


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In fact electroless nickel coating on steel is definitely harder, but this depends on what you are trying to achieve: just hardness or hardness and appearance. Cold solutions with sodium borohydrate as a reducer provide Ni-B alloy, which is hard, but dull and grey in appearance, while hot bath with sodium hypophosphite results in Ni-P alloy which has better leveling power and more glossy. Both types of coating require heattreatment, otherwise hydrogen will penetrate in steel and cause microcracks.

However you can rise hardness of electroplated nickel in standard Watts' bath by adding Ferrous iron ions - 1-3 g/L. In this case heattreatment is also required to avoid tensiles (iron tends to plate first and internal layers of the deposit contain less nickel than external, if iron concentration is not kept constant).

Anton Cheglov
- Brisbane, QLD - Australia



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