NO-OX-ID A-Special- Electrical Contact Grease- Keeps Metals Free of Rust and Corrosion- Part# 10203

Anodization / paint / powder coat is an electrical insulator. Grind it off the mounting plate where the ground side of the antenna mount and around all bolt holes, and then apply no-ox-id on and around the exposed metal and bolt threads. It would also help you to run a grounding strap, as they are far better at grounding an antenna than simple wire. I would also use different coax, rg-316 works quite good on vehicles with the short runs and is very easy to fish theough small holes. Also make sure you've got the mounting stud on correctly.