I'm going out on a limb to say you're probably using a wheel cleaner that's leeching under the clear coat. I'm guessing that because the upper spot of corrosion on the rim has a spot on the logo cap next to it. Again, only guessing, but maybe wheel cleaner is getting behind the cap and getting slung out when you drive.
It's definitely not a safety issue. You'll have to remove the clear coat to get rid of it, and the wheel will never look the same. I've fixed the same thing by carefully sanding the clear off the shinier surface and then polishing it, but it ended up looking more like chrome than brushed aluminum. I bought a slightly damaged wheel for $25 (Visibly damaged but still true and safe) to test it on and liked the look on my truck, and kept the wheel as a full-size spare.