Just a tip here - I've used this self etching primer rattle cans on some small parts that I've had to take down to bare metal and it works great. Plus, it turns out to be a pretty nice olive drab color... https://amzn.com/B003CT498A (But it's only 5 bucks at Home Depot)
[h=1]Rust-Oleum 249322 Automotive 12-Ounce Self Etching Primer Spray[/h]
[h=1]Rust-Oleum 249322 Automotive 12-Ounce Self Etching Primer Spray[/h]