Dawid, please send me your e-mail (again?).
Cedric, I used mild steel and galvanized it. Not only cheaper, but easier to work with. Stainless would probably be the "ideal" material for this one though, but it's more difficult to find the square tubing that the legs are made from, and more difficult to weld (the steps are made in two pieces which are welded together).
Mag ons ons kenniskry met lekkerkry aanhoukry.