Corrosive nature of Iphone XR's aluminum body

Its been more than a year since I bought my bright yellow iPhone XR from an Apple retailer in India and I'm noticing these weird micro dents and holes from my phone's aluminium frame and especially more near the charging port and around the camera lens (not sure whether is it due to corrosion, abrasion or something else but doesn't look like paint chipping) which is gradually spreading fast and is really a huge point of concern for me since I'm worried about my phone's durability in the coming years. I do use a silicon back case and am not a rough user. Wanted to know the reason for this issue and any possible solutions. Thanks in advance.