When sourcing iron buckles, the material grade is paramount. Ensure the supplier uses Q235 or higher-grade carbon steel for general applications, or stainless steel (304/316) for corrosive environments. Surface treatment is critical for longevity; look for Electro-galvanized (zinc plating) for indoor use, Hot-dip galvanized for outdoor durability, or Electrophoretic coating (ED coating) for a high-quality black finish. Always verify the salt spray test hours (e.g., 48h, 72h, or 96h) to ensure rust resistance meets your specific climate requirements.