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"Conductivity of Zinc and Zinc-Nickel Plating"

Current question:

June 20, 2021

Q. How to achieve conductivity -Resistance value within 2.5 milli-ohms on Zinc Nickel plated connectors connected to braid or cable with 2 inch length.

Zinc nickel plating is done with an undercoat of Electroless Nickel. Base material is Aluminum 60 series.

Satheesh kumar .R
- Bangalore karnataka India

June 2021

A. Hi Satheesh. Zinc-nickel and electroless are quite conductive, but the chromates used on them are not. You should try the thinnest, clearest chromate available, with no topcoat. Unfortunately, this will probably adversely affect the corrosion resistance; but with electroless nickel underneath, maybe it will be okay.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

July 3, 2021

Q. Hi, thanks for your ideas. Yes we have already made top coat layer thinnest by reducing concentration and process time by which we have achieved electrical resistance less than 10 milli ohms, but still we need to achieve less than 2.5 milli ohms consistently for our connectors used in aerospace applications.
Any specific parameters to be adjusted in Zinc Nickel Plating bath?
What is oven baking process temp & time to be maintained after chrome passivation?sp

satheesh kumar .R [returning]
- Bangalore karnataka India

July 2021

A. Hi again. I've heard of measuring the resistivity of type III chromate conversion coatings on aluminum per MIL-DTL-81706, but sorry I'm not familiar with similar requirements for zinc-nickel plating and chromate conversion coatings. But your units don't seem right as they lack an area and a pressure (MIL-DTL-81706 requires not greater than 5000 microhms per square inch at a contact pressure of 200 psi). Is any particular machinery described for your test? The referenced documents notes that the surface roughness of the item being tested and of the electrode pads can have a greater effect on the reading than the thickness of the coating.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Closely related historical postings, oldest first:


Q. Is Zinc Plating conductive? If not, what plating is ?

Thank you,

Sharon Nicodemus
Rittal - Springfield, Ohio, USA


A. The zinc itself is conductive, however, conventional chromate conversion coatings add surface resistance that lower the anticipated conductivity of pure zinc. Furthermore, organic topcoats and other sealers intended to boost the corrosion resistance of chromated zinc typically degrade the surface conductance even further.

milt stevenson jr.
Milt Stevenson, Jr.
Anoplate Corporation
supporting advertiser 
Syracuse, New York

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A. Zinc in itself is very conductive, the chromates applied after plating for corrosion resistance do offer some electrical resistance. The "clear" or colorless chromate is the most conductive. ASTM B633 [affil. link to spec at Techstreet] Type III

Bill Grayson
- Santa Cruz, California, USA

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