I plan on building an arbor with 2" square, white, tubing ( the sort used for screen rooms). I read that aluminum should not be set in concrete. What if is used 2" X 2" PT wood set in concrete and put the aluminum post over them? Any comments appreciated
Wood that thin doesn't offer much in the way of strength or stiffness. Even if you built your arbor as a completely self-supporting structure and only needed the posts to anchor it, 2x2s would offer relatively little in the way of storm resistance, for example.
A better approach is to design your arbor so that it's self-supporting and rigid, and mount stainless steel brackets to the slab using suitable anchors. Your arbor's legs would attach to the brackets. They won't offer torsional stiffness, but they'll keep the arbor in place.
You could also embed pipes in the slab, into which you'd insert your aluminum legs. These could be PVC. You'd then use shims to secure the legs of your arbor into them. The pipes should be open at the bottom with a drainage basin of sand or washed rock.
First: Answers are the goal here not comments. Please phrase your post to have a clear question that can be answered, not just say "Any comments appreciated"
2x2 ( 1 1/2" x 1 1/2" ) are not very strong. Cladding them with metal will trap moisture.
1: Use steel in the ground, ( square post anchor ) stubbed out just above ground level like stop signs, and slip the aluminum over or into the steel and bolt it on.
2: Use the expanding foam products that are now available to replace concrete for fence post installation. The one website i looked at said it could be used with "metal". Do some research.