Rust on new irons - a bit surprised

That will.prob just wipe off with a wire brush. I got a few spots on mine when they were in the car for a few hours after playing up a Brora earlier in the year. I'd imagine mizuno or the place you bought them from will replace them. But in reality they are for hitting things, it's shouldn't happen but is does, it won't effect the performance,its only cosmetic after all