Some natural fresh water sources may contain high amounts of minerals, especially in areas with lots of limestone. Rinsing the rim and spokes in fresh water may be a good idea (although my old rural home's two water wells had more limestone content than the nearby lake, especially after fracking disturbed the entire area's limestone aquifer).
After removing the tires, tubes, rim strips, etc., dribble in a drop of Boeshield T9 or WD40 around the spoke nipples and holes. Either will displace water and resist corrosion. It'll also make it easier later to do spoke nipple adjustments for truing. Otherwise the entire spokes may twist along with the nipples.