I'm just finishing scrubbing hard water stain off 2,016 2" tiles in a tub/shower enclosure, and I will never do that again!! Does anyone know of a treatment or protective coating you can apply to ceramic tile to prevent hard water minerals from bonding to the surface? Has anyone tried something like car wax, by any chance?

Go to any home improvement center and buy some tile sealer. I just sealed my countertops that we just got done tiling. It's made just for those reasons.

Home Depot sells a product called GEL-GLOSS. It is located by the tubs and sinks. It goes on like car wax and you buff it out. I use it on my tiled countertops and fiberglass surround.

I had ceramic tile in my shower and as a quick fix I used car wax.
Beads up well and lasts for about 10 or so showers.