What is "Steelduct"

[SQLit]

We used to get "steel duct" for culverts in the Midwest. Galvanized inside and out.

[toller]

I am making a composter, and I have a piece of "steelduct" that would be perfect, but it will be used outside and I am concerned about rust.

I don't know what steelduct is and a search didn't turn anything up. It "looks" like galvenized steel conduit; but I am hoping someone actually knows. If it is galvanized, is it galvanized on the inside also, or just the outside? Thanks.

[toller]

Then I got lucky! Thanks