Or sandblasting from motorway runs. Most other cars I've had recently have had an undertray. Makes draining the oil a pain but gives some protection. My 500X has one, can't remember if the 500 TA (2011) that preceded it also had one. Not seen any reports of TA sumps rusting.

Bought our 59 plate in 2015, the supplying non Fiat dealer replaced the sump as they noticed it either extremely rusty or leaking FOC and a new battery that didn't seem that bad when test driving, new discs and pads as they were appallingly rusted( as too were the rear drums and front shocks)