This is a dumb question for any Mirage owner with steel wheels and plastic wheel covers...
I've noticed this about almost every new car with steel wheels... The wheel paint seems to be either really cheap or non-resistant to UV light (or both). You can look at almost any new car with hubcaps and see the wheel rusting in the area not covered by the wheel covers (see pic below). I assume the Mirage is no different?
View my fuel log 2015 Mirage ES 1.2 manual: 51.6 mpg (US) ... 21.9 km/L ... 4.6 L/100 km ... 62.0 mpg (Imp)