If they touch the steel hoop can cause galvanic corrosion in the aluminium which you will never get rid of once its in the grain.
It won’t stop once it is started even if the connection is interrupted?
MOG42 said you'll never get rid of the effect, not that it wouldn't stop if the cause was isolated.
Once the more galvanically reactive metal (in this case aluminium) has formed oxides or hydroxides due to electron loss these products are not just a superficial coating - the characteristic milky discolouration goes into the grain of the metal and needs a proper refurb and not just a surface polish.
I lost too many fancy three-piece rims to this phenomenon in the '90s - now I see my son lusting after exactly the same expensive bling. How come we never learn?
