Ned Simmons wrote:

Almost all square structural tubing is ASTM A500 steel and doesn't
require a low hydrogen (xx18) rod. Unless the tube is something
exotic, or there's some code requirement, I'd use 1/8" 6010 (DC) or
6011 (AC). They're both all-position rods and easier to run than 7018.
But if the 7018 is handy...

Hi Ned, I don't know if it is structural, but my local supplier refers to it
as "hot formed", if that helps.

My reasoning for choosing the 7018AC was for it's less brittle qualities.
It is most likely overkill for the application, but I figure if I can get
the hang of it after some burning some rods up in practice, it wouldn't
hurt.

Jon