ArtMetal

I'm currently working on a rail that is to be installed in a pre cored retaining wall with 3" dia. and 8" depth for posting. The stancheons are 1" sq. tube 1/8" wall.I generally use mechanical fasteners but since the holes were there and on fairly accurate 6' centres I decided totake advantage of them....... Question: what is the best mortar/concrete to use and should the metal (aside from being powder coated) be treated with some type of coating for longevity.
The bottom of the stancheons are open and the tops where they meet the top rail are %100 welded. One reason I'm concerned is some rail on an apartment I occasionaly repair which is set in sometype of dense dark grey concrete like (?)fixative has horrid corrosion, and although the welding on these is extremely shoddy ( ie. incomplete fusion, holes in welds, excessive porosity allowing water to get in from the top)I wonder if the installation into the fixative was suspect? These existing rails are no older than 30 years old.

Since I'm on a wordy tangent I have two other querries,

One is that of distortion correction or prevention techniques or literature that aren't directed towards ship builders and the like ( has anyone ever used Wagners 3 chock straightener?)

Two, possibly the unanswerable one that of bidding or pricing standards for non-commercial architectural metal?

Pointing me in any direction for any of these would be greatly appreciated.

Thank you