Letter 3031

Electrical Grounding of Anodized Parts 

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I have anodized aluminum components that I wish to attach a grounding strap to. I understand that anodizing is a good electrical insulator as well as providing corrosion prevention. What is the best way to attach the grounding strap to achieve electrical requirements while also preventing local corrosion where the strap attaches?

Bob Kozero
Orbital - Dulles, VA

June 9 -

This is typically how it is done: After cleaning the aluminum and prior to anodizing, mask off the area with a masking dot or some such maskant. Anodize. After completing the anodize process, remove masking dot, and chem-film (chromate)masked off area.After a four hour cure not to exceed 140 degrees, you may attach your grounding strap.

Ward Barcafer CEF
- Wichita, KS

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June 9 -

There are several options. One is to chemfilm (Alodine) the part and mask off the area that you want for the contact point. Then anodize the part. Remove the masking and attach the contact. If necessary, you can bleach the spot with hot water to make it more conductive. The reverse process is possible. Mask and anodize. Spot chemfilm the desired area. This has some problems as it is messy and if the aluminum is not "new" you will have to clean and activate the spot. Normally this causes damage to the nearby anodize. You could anodize and grind off the anodize on the spot. This will take chemfilm well if done immediately. If it is thin anodize, you may be able to break thru the anodize with star washers on both sides.

James Watts
- FL

To achieve electrical contact on anodized parts, another option is to anodize the part completely, then laser etch off the anodizing in the area needed for conductivity. It produces a clean line and can be used in recessed areas (such as countersunk holes). Chromate conversion coating can then be used to provide corrosion protection on the lasered area. We have had great success with this process on electrical parts.

Laura Friedrich
- Delta, BC

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