The new feeders I have are all plastic with a built in ant guard. If you don't have an ant guard in my area the feeder gets full of ants in a very shot time. i'm amazed that they can find their way up a tree to the feeder.
I had an ant problem big time. My feeder hangs from a bracket that is attached to the eaves of the house.

I used vaseline on the bracket starting from where it is attached to the wall and was liberal with smearing it on.

It has stopped the ants so you might try it.