It really depends on your particular environment, if aluminum is subject to surface corrosion in your area, I would suggest getting some kind of coating on them, or you will be cleaning the rims probably more often than you would like.
Powder coating is an option as well, Iv'e heard that there are two processes, one is a lower temp process, and is recommended for rims like the R65 has, and then there is the standard powder coating that uses temps in the 400 F. range, and subjecting your rims to that kind of heat I have read is not recommended.