The descriptive text that displays during map loads says that Corruptor arrows turn a machine hostile to ANY other machine. However, I just shot a Longleg with a Corruptor arrow, and it was standing right next to another Longleg and it did not turn hostile toward the other. What am I missing?
To corrupt a machine by the use of corruption arrows, you will need to fill up the corruption meter. It will appear once you managed to hit an arrow on your target. The symbol will be a gree circular UI element with a spiral in it.
You will need to hit corruption arrows until the green part is filled up all the way. Then a white ring will appear around it to indicate that the corruption debuff is applied on the enemy.
You will not be able to corrupt machines that are already corrupted in a different way (e.g. in a Corruption Zone). Also, Daemonic Machines are immune to it (those are the ones with purple markings on them). Furthermore notice that different machines may have different resistances to this debuff.
I am not sure, but distance may also affect how much an arrow will fill up the meter.