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Best spec for Electroless Nickel Finish for Zinc Diecast Part

I have a zinc diecast part (connector backshell) and I want to specify an electroless nickel finish on the part. What specification (MIL-C-26074 [on DLA], ASTM B656 [withdrawn 2000], ASTM B733, AMS2404, AMS2405 ) is more widely used for zinc parts? How does one specify the thickness and/or the heat treatment for the finish (I'm too cheap to buy the specifications)?

I am thinking that I would use a low or medium phosphorus type (less resistance for emi purposes) with no heat treatment (maybe cheaper?). Since the part is zinc, do I have to copper flash the part? What would be the best callout for that process? I am looking for the most cost effective solution for the part. Thanks for any help you might be able to provide.

John B [last name deleted for privacy by Editor]
- Rohnert Park, California
1999

Hi, John. Yes, you may need a copper flash before the electroless nickel, although an alkaline electroless nickel strike may be an alternative.

Pick a local plating shop that claims to do electroless nickel on zinc diecastings, then sit with them to plan the process and write a plating specification. Nobody can afford to write that the plating shall comply with a spec that they haven't seen :-)

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 28, 2009