My brakes make a dragging sound like the brake pads are not fully disengaging from the brake disk. The cause?

It is not a very loud drag but it is noticeable. From the sound, I picture it as the brake pad(s) still making contact with the disk, well after the brake pedal is released. The car was purchased from Maine, so I can see that the salt has left it's mark, since the brake calipers are a rusty brown, on the outside. Is it likely that replacing the calipers, would fix the problem, or could this be a brake hydraulic problem?