Third-seeded Thomaz Bellucci was 2, 7-5.
Del Bonis broke Bellucci four times from five opportunities and dropped serve just once to claim the win in one hour and 31 minutes
He moves on to face seventh-seeded countryman Carlos Berlocq, who defeated Diego Junqueira 6-1, 6-0 in 62 minutes.
Meanwhile, No. 2 seed Juan Ignacio Chela defeated Horacio Zeballos, 6-4, 7-6 (7-2) to advance to the quarterfinals. Chela will face Joao Souza of Brazil, who defeated local wild card Fernando Gonzalez in straight sets 6-3, 7-6 (8-6).
Also on Friday, top-seeded Juan Monaco will look to advance to the semifinals as he takes on fifth-seeded Albert Montanes of Spain. Monaco made it all the way to the finals in 2010 but was ousted by Bellucci in Santiago.
The 2012 Vina del Mar champion will collect $71,900.