Outer Limits 4x4 Board

I guess, I'm not the first one to encounter this problem:
I have an aluminium bullbar and need to mount a HF aerial which requires earthing.
Therefore, I mounted the steel spring base directly to the bracket on my bullbar.
I noticed that the aluminium stared to corrode quickly.

What do people do to prevent this from happening? I was looking for a material or paste which conducts well and prevents galvanic corrosion.

Thanks
Joachim

Nylon washer both sides. Use seperate earth lead from under base back to chassis.

Bazzle

Cool

Thanks Bazzle