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Do not alodine that bare aluminum. Alodine is a substrate adhesion treatment for aluminum before you prime with a zinc primer. Its colorless- Look up alodine 1200. Touch up alodine ( Aircraft materials processing)

The only way to repair this is to re-anodize the bare surfaces. This can be accomplished at home by making a sulphuric acid bath 20% battery grade sulphuric acid and 80% distilled water ( add acid to the water- not water to the acid. You don't want to know why... ( use something inert like polypropylene for the containment or glass) You can get a battery charger and create a anode and cathode with the leads. Immerse the center of the wheel in the acid dillution and attach the positive lead to the aluminum steering wheel and make electrical contact. Connect the negative lead to a lead tire weight and put it in the bath. Make sure to degrease the exposed bare aluminum ( This is why you cant alodine over irridite or alodine...It will act as a maskant) set up the bath and turn on the battery charger of low ~2 amps @ 12V. increase current and watch you aluminum bubble ~ Hour or so.......Rinse thoroughly with water...Now you can get out the sharpie and touch up the aluminum for a permanent anodizing...Or buy some anodizing dye...all colors are available besides black.

Hope that helps