The rusty steel pipe is for the power steering. The other pipes, which are aluminium, not stainless steel, are for the A/C.
A point of interest here for V6 owners: a little further towards the n/s than your photo shows (i.e. to the right in the picture) these pipes pass very close to one another, and quite often they are touching. This is not good as after a while the steel PAS pipe will actually rub through the soft aluminium A/C pipe, causing you to lose your A/C gas. It's advisable to wrap something round the A/C pipe in order to protect it, such as a short length of rubber hose, slit along its' length in order to fit over the pipe, and secured in place with a couple of cable ties.
Whilst under the car, check the condition of the engine oil cooler pipes; these are a common failure due to corrosion, and the consequences can be disastrous.