Using “old” 5W iPhone 5 Power adapter to charge a new iPhone XR
I would like to know if it is safe to use an “old” 5W Power Adapter (charging brick) from an iPhone 5 to charge my new iPhone XR.


Yes.


  Is it necessary to purchase a new charging brick?


No.


  Could the “old” charging brick damage my new phone (since it is too old)?


No. As it is working fine with an iPhone 5, it will be fine to use it with iPhone XR.



So, yes, it will be fine using the old power adapter from your iPhone 5 to charge your iPhone XR.