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EN heat treatment on zamak

October 13, 2009

Hello,

For our project, we're trying to find a suitable plating, corrosion and wear resistant, conductive and good looking, for our zamak 5 parts.
We tried electrodeposited CuNiCr and to tell the truth is fits well our need regarding corrosion resistance and wear resistance.
Unfortunately, because electrodeposited plating do penetrate inside hole (our part looks like a tube) we've got wear and corrosion problems inside the parts where a stainless steel latch slides against the almost bare zamak surface.

Today we're trying high P electroless nickel, 10-20µm (but I'm pretty sure it won't be thick enough) and 20-40µm. Still we have some wear problem then we're thinking about increasing the EN hardness with a heat treatment.
Then, my question is: What heat treatment shall I do?
I of course don't want to deform the Zamak5 thin walled box shaped part with quite tight tolerance.
My last idea was to heat the part at 260°C (500°F) for four hours acc to MIL-C26047E but I don't what I'll have at the end. If I reduce further the Temperature will I reach the maximum hardness? Is there charts existing? What if I make the heat treatment in a conventional oven, will it work?
Many many thanks in advance for your answers.

Bertrand Dauchelle
product designer - Paris, France

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There are charts that relate temperature vs. hardness but you need to know the Phosphorous content. Four hours at 260o C will give about 850-900HV if the deposit has between 10-12% P content. Get a good book or manual about plating.

Guillermo Marrufo
Monterrey, NL, Mexico
October 15, 2009

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First of two simultaneous responses --

Depending on what your corrosion cause is, alkaline EN is harder than acid EN without the heat treat. Different formulations have different values. EN vendors can provide this information.

James Watts
- Navarre, Florida
October 16, 2009

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Second of two simultaneous responses -- October 19, 2009

Hello,

thanks for the answer.
I know I should buy a book but I sometime prefer rely on the plater's experience. Unfortunatley looks like every case is new for them and then only answer is to test.
I put my zamak part in an oven for 4 hours, I think I'll forget the idea to harden my High P EN, the part got all deformed and the plating doesn't stick anymore to the part.
250°C is way to high for Zamak I suppose. (melting T° is 400°C)

Bertrand Dauchelle
- Paris, France