You may destroy the head, but I don't think you'll break it. When the screw breaks loose, I think you'll tear out some of the aluminum frame! At best, you'll be able to reinstall with the same size screw - maybe not.
I'm thinking back to the spinnaker track on the previous boat. Stainless flat bar for track, aluminum spacer, fastened to aluminum mast with stainless fasteners. The corrosion between the track and the spacer was so bad the track buckled to the point the car would move. Managed to remove the fasteners with an impact screwdriver, cleaned up the corrosion with a wire brush, flattened the track, reinstalled with electrical tape between the track and the spacer - no more problems.