Quick Answer The most suitable materials for outdoor radar tower structures are high-strength low-alloy (HSLA) structural steels, specifically Q355B (equivalent to ASTM A572 Grade 50 or EN S355JR) and Q235B (equivalent to ASTM A36) for secondary members. These steels offer an optimal balance of yield strength (minimum 345–355 MPa), weldability, and toughness. To withstand environmental corro...