Kaymer is at 12-under 132 after 36 holes and moved from a tie for sixth into the lead by three strokes. First-round leader Charl Schwartzel is alone in second at 9-under 135. He shot 1-under 71.
Graeme McDowell (70) is in third, four strokes behind Kaymer. Rafa Echenique (68), Niclas Fasth (71) and David Lynn (68) are tied for fourth at 7-under 137.
Windy and rains conditions affected play, as shown by Schwartzel's six-birdie, five-bogey round. Kaymer had the only bogey-free round among the top 49 players Friday, although Ricardo Gonzalez (68) erased his back-to-back bogeys at Nos. 5-6 with a hole-in-one on the par-3, 200-yard seventh hole. He is tied for 19th.
Kaymer started on the back nine and was 2-under after five holes. He opened his second nine with a birdie at No. 1, got to 4-under with a third-hole birdie and took the lead with consecutive birdies on Nos. 5-7.