Do not cheap out on the coating or the wall thickness. Your carport is protecting a $30,000+ vehicle. A $200 difference in steel is nothing compared to a collapsed roof five years from now.
Open Google Maps right now and search: “Steel supply near me.” Then call and ask for their 2.5” x 2.5” x 12-gauge hot-dipped galvanized tube. Have a tip on a great local steel yard? Share it in the comments to help other DIYers in your area.
The Ultimate Guide to 2.5” Galvanized Square Tubing for Carports: Sourcing, Strength, and Local Buying Tips