Astronauts Rex Walheim and Hans Schlegel completed the second of STS-122's three scheduled spacewalks at 4:12 p.m. EST. The excursion lasted 6 hours and 45 minutes.

The spacewalkers completed the removal of an expended Nitrogen Tank Assembly (NTA) and the installation of a new one on the P1 truss. The tank is part of the orbital outpost's cooling system.

With the help of the station's robotic arm, the spacewalkers moved the new NTA from its position in space shuttle Atlantis' payload bay. They temporarily stowed it on a Crew and Equipment Translation Aid cart while they removed the expended tank. With the new NTA installed, the old tank was transferred to the orbiter's payload bay for return to Earth.