Second-seeded Peng Shuai was taken to opening ASB Classic tennis 6, 6-3, 6-4.
Arn won last year's ASB Classic with a victory in the finals over Yanina Wickmayer, who is seeded seventh this year and downed Karolina Pliskova, 6-3, 6-4, on Tuesday.
In other ranked action on the hardcourts at ASB Tennis Centre: No. 3 Svetlana Kuznetsova defeated Alison Riske, 6-3, 6-2; Roberta Vinci, seeded sixth, took out Rebecca Marino, 7-5, 6-4; and No. 8 Monica Niculescu breezed past Jamie Hampton, 7-6 (7-1), 6-1.
The winner of this $220,000 Australian Open tuneup will claim $37,000.