Asking for a friend...

The image below is part of a steel weather vane. As you can see, it's rusty and
getting worse. My friend wants to remove the rust then clear coat the piece to
prevent the rust from coming back.

You can't really tell from the image, but there appears to already be some type
of (uneven) clear coat on the piece already.

What's the process to remove the rust and existing coating without damaging the
metal and what's the proper product to prevent the rust from coming back?

https://i.imgur.com/bk3eTz5.jpg

Thanks!