Livewire forward Irankunda struck twice in a five-minute burst from 80 minutes as the Socceroos ran riot with four goals after the break against the smallest country to qualify for the World Cup finals.
Jordy Bos and Alessandro Circati also grabbed second-half goals at Melbourne Rectangular Stadium after Curacao’s Arjany Martha scored for the visitors on 50 minutes, cancelling out Awer Mabil’s 23rd-minute strike.
It was a more reassuring performance for the Socceroos, who won struggled in a stodgy 1-0 win over Cameroon in a friendly on Friday.
They were also disjointed for much of the first half, struggling with forward transition and needing keeper Mat Ryan to save them twice.
However, they settled after 23 minutes with a touch of fortune.
Kai Trewin pressed forward and swooped on a loose pass from Curacao captain Leandro Bacuna, sending a cross in to Deni Juric, whose back-heel took a kind deflection off a defender, allowing Mabil to poke the ball into the right corner.
Ryan was forced into a fine save before the break when a Bacuna through ball found Jeremy Antonisse who sent a low shot into the diving keeper’s arms.
The Socceroos nearly doubled their lead on 43 minutes when Hrustic curled in a long cross to Mabil but his volley thumped into the right post.
Curacao started the second half brimming with energy and were rewarded after 50 minutes when substitute Gervane Kastaneer headed the ball to release Martha who streamed forward and beat Ryan one-on-one with a low shot.
However, Circati responded 17 minutes later with his first international goal, diving in for a header after a curling cross from Riley McGree.
Bos, who scored in the win over Cameroon, produced a lovely finish, curling in a right-footed shot.
Substitute Irankunda, injected in the second half, wrapped up the match with a flourish, using quick feet to beat defender Jurien Gaari before smashing a fierce shot that deflected off keeper Eloy Room and rolled into the net.
Four minutes later, he soaked up another round of cheers from home fans with a crisp finish into the left corner.
Australia play their opening World Cup match on June 13 against Kosovo or Turkey, who meet in a playoff later on Tuesday.