I brought this back up because it works as an addition to screwylouie's tip.
I posted this somewhere before..after cleaning the wheel with BKF, try Dupont granite and marble sealer. Spray it on a rag wipe it on the wheel, let it sit ~ 15 minutes and buff dry with a dry microfiber cloth. I treated my back wheel prior to the Salt Springs trip and just wiped the wheel down the other day, shines like it was new with very little effort. The sealer is somewhat pricey, Lowes for about $14-16.