If you are getting it for free it may not be a bad idea, but even if it 22ga or lighter it is going to be pricey. Something to consider though, you would have a smother surface to reflect light better due to its rigidity, unlike mylar film which can wrinkle a such. Then again considering the smooth and polished finish it may act like a magnifying glass and burn the plants. If you notice may light reflectors are brushed aluminum sheet or polished aluminum with a crinkled surface.