When sourcing steel shade structures, the primary focus should be on the grade of steel and the anti-corrosion treatment. For structural integrity, Q235 or Q345 carbon steel is the industry standard. To ensure longevity, especially in coastal or high-humidity areas, specify Hot-Dip Galvanization (ISO 1461) with a coating thickness of at least 85μm. For the roof cladding, look for color-coated steel sheets (PPGI) or polycarbonate panels with a minimum thickness of 0.5mm and UV-resistant coating to prevent yellowing and brittleness.