If it is possible, why not get rid of the calcium chloride that I assume you have, sand down the rusty area, repaint and put the non-corrosive RimGuard back in for weight; provided it's not rusted through to where it casn't be readily sealed.
Just out of curiosity and for my own knowledge, how long has that fluid been in. I had wheels rusted around the valve stem that stayed that way for many years, they still worked but it's not pretty.