My RRS 20" black rims developed a slow leak. I took it to a tire shop and they discovered it was some corrosion near the bead and the coating was flaking off in large chunks. They scraped off what was loose and put the ires back on. They said it was likely I will be back in 3-6 months with another slow leak and perhaps the other wheels will develop it too.

My RRS is a 2016 with 16K miles. It has been driven in the the NYC/Boston area and kept in a garage. Is this normal or do I have defective rims?

Here are pictures of the wheels and the coating that is flaking off at the bead.