The Russian was broken in her first service game but recovered to win in just 63 minutes.
Play was suspended on Tuesday because of torrential rain, meaning 12 matches had to be completed Wednesday. Petrova will next play Vania King of the United States, who beat Alberta Brianti of Italy 6-4, 7-5.
Story continues below ↓advertisement | your ad hereSecond-seeded Anastasia Pavlyuchenkova of Russia overcame Australia's Anastasia Rodionova 7-6 (6), 6-1 while third-seeded Maria Kirilenko ousted Urszula Radwanska of Poland 6-3, 6-1.
No. 4 Maria-Jose Martinez of Spain, No. 6 Yaroslava Shvedova of Kazakhstan and No. 8 Agnes Szavay of Hungary also advanced.
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