To the automotive advice columnist

I have been thinking of planting a small garden or number of garden areas on my mid-size car. Well, not technically gardens, but square plots of grass. I think I'd like to place a square of turf, perhaps 2.25 square feet in size on the hood, a similar, though smaller, square on the trunk, and a larger square (or perhaps a rectangle) on the roof. In order to do this, I intend to weld metal strips of perhaps two or three inches in height to the car's surface to serve as borders to the grass and soil. My question: can you suggest materials I might treat the present surface of the vehicle with to prevent corrosion? Secondly, do you think that two inches of soil will be enough to support the continued growth of a lush surface of grass? Well, perhaps that is really a question for the gardening column. I appreciate your advice in this matter.