... can reach 83.3%, which is as twice as cast iron.3.Galvanized surface: rust-proof, anti-corrosion,Maintenance convenient.4.Economical ... and Japanese standards are available. The products most commonly used for Belt corridor, storage shelf,Attic panel, trestle, guardrail, sunshade ... and surface treatment. 4. If any enquiries, please contact us. galvanized steel trench cover for rain draining system