When sourcing iron square tube gates, the wall thickness of the tube is the most critical factor for structural integrity; for standard residential use, a thickness of 1.5mm to 2.0mm is recommended, while commercial gates should exceed 3.0mm. Additionally, ensure the iron is Hot-Dip Galvanized rather than just cold-galvanized to provide superior corrosion resistance and a lifespan of over 20 years in outdoor environments. The welding technique should be full-seam welding rather than spot welding to prevent water ingress and internal rusting.