Many tank wreckages can be found at the Metal Head nest, although they are slightly different in appearance. It is assumed they were an older design and were destroyed by Metal Heads during a previous assault on the nest.
They are first encountered in the early "Blow up ammo at fortress" mission of Jak II where you must out-run the security tank and stay out of its cross-hairs. You must move frequently during this mission especially when the target closes in or you will be blasted into a crisp or sliced by the spikes on the tank. While trying to evade the tank, the camera shifts to a first person perspective of the tank (similar to the camera perspective when fighting the robotic snipers in Jak 3). When you outmaneuver the tank the camera changes back to normal. Staying further away is the best way to avoid it; the cannons are not very accurate, so roll-jumping is a good method for evading them. The roller is easily avoided by simply staying away from it.
The security tank can be seen in the floating KG war factory when in the flying sequence, firing on the player from road-like tracks on the inner platforms. They do little more than average damage compared to other enemies in the sequence. They do not have any other role in Jak 3 and do not behave like they did in Jak II, and do not require much evasion tactics more than just ignoring them.