[pHaestus]

I wouldn't expect any salt crystals to form. Iodide should be pretty soluble in 25-30C water, and the antifreeze will keep cations complexed that would otherwise complex with it.

It's somewhat redox active though and oxidizes from I- (-1) to IO3- (+5). So in principle I- could also dump those electrons in your loop by attacking aluminum oxide coatings (e.g. anodizing) and reducing them. That wouldn't be a problem initially, but that could drive the deterioration of the anodized layer as the aluminum oxide that eventually forms won't be as stable as the anodized surface. I don't know all the redox half potentials off the top of my head though so I don't know if this is a realistic concern in a typical loop we'd use. I seem to recall something about anodized surfaces still slowly corroding and releasing Al3+ in seawater though (which contains a good bit of iodide).