Gonzalez began the day one-stroke back of first-round leader Lee Slattery of England and his round Friday was marred only by a bogey at the par-4 seventh.
Six birdies secured his spot atop the leader board.
"It's been some time since I put two rounds together," the 39-year-old Gonzalez said through a translator. "(But) the golf's still there."
Gonzalez has not won since 2004 and has risen to 316th in the latest world rankings.
Slattery shot 3-under 70 Friday and is second at 9-under 137 through 36 holes.
Sweden's Martin Erlandsson (70), Spain's Pablo Larrazabal (71) and Scotland's Richie Ramsay (70) are tied for third at 6-under 140.
Sweden's Peter Hanson (73), the defending champion, is 1-over 147, tied for 51st place.