Welding Tips and Tricks

I want to build a long arbor in my backyard, and I want to build it out of metal. What type of metal should I use to make it last? Thanks for the help.

If you are leaving unpainted/uncoated, then Corten, stainless or aluminum.
If you going to paint/powder coat it, then mild steel tubing works perfectly well.

Many arbor designs have arched segments for which you will need a ring-roller to prevent the tube from collapsing.

Or you can make it from wood and avoid all this mess

Does anyone have an idea how well 6061 will do in contact with the ground?
Fairly wet part of the country.