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Zinc plating for EMI Grounding

I'm trying to improve my finishing spec to plate 0.030" thick cold rolled carbon steel sheet 1/2 hard temper, for EMI grounding. It was suggested to use the following. "Inorganic/chemical surface finish: Zinc plating with single dip clear chromate & no lacquer finish, for EMI grounding. Minimum thickness: 12.7 µm or 0.0005". Surface resistance: 1.0 ohms max." Can platers meet this spec?

Maurizio Palluconi
- Rochester, New York

Is the sheet being formed into something before plating or do you intend to have this plated on a coil coating line?

I would leave out "Inorganic/chemical", not necessary to say this. and 'for EMI grounding' The plater won't say that his finish will satisfy your grounding requirements since he is not acting as an electrical engineer.

0.0005" This is a little thick as a minimum, depending on the shape of the part, and where you will specify a significant surface. Surface resistance: 1.0 ohms max.: I would specify the test and test probe in writing.

Tom Pullizzi
Falls Township, Pennsylvania

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The sheet metal is highly conductive as well as the zinc. Unless the clear chromate interferes, you should get very low resistance. Here zinc is not the EMI shield but the sheet metal itself is. Zinc only provides corrosion resistance. Also the resistance needs to be defined with distance between to points on the finished product where the measurements are made. Your customer should define it so that you can measure it using a multimeter.

Mandar Sunthankar
- Fort Collins, Colorado

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