Forgot to mention, but we are actually replacing faded covers and that's when all of the rust was discovered. One of the guys got a little too agressive with the prep and now a couple are leaning against the building.
We've straighten up a few that have gotten push over by putting a chain at the top and gave them a little pull. We seal them with foam in a can so they can't be lifted off and grow legs and walk away.
I just drilled some holes with the hammer drill, pounded in some rebar, and used a new section of pipe I had laying around. When the concrete cured it was as solid as the original bollard. I covered it with a plastic bollard cover. No one will ever know!