Q355GNH demonstrates outstanding corrosion resistance in high-humidity industrial atmospheres, significantly outperforming conventional structural steels. Laboratory studies confirm that the atmospheric corrosion resistance index of Q355GNH reaches 7.13—far exceeding standard requirements. Under identical corrosion conditions, the average relative corrosion rate of Q355GNH is only 47.40% that of Q345B steel, a commonly used structural grade.
This superior performance stems from the alloy design based on copper (Cu) and phosphorus (P), with additions of chromium (Cr) and nickel (Ni). These elements promote the formation of a dense, flocculent rust layer rich in protective α-FeOOH (18.2%) and Fe₃O₄ (9.1%). This stable oxide film effectively blocks oxygen and moisture penetration, dramatically slowing the corrosion process. In industrial or coastal environments, Q355GNH exhibits typical corrosion rates of 0.02–0.04 mm/year, compared to 0.12–0.20 mm/year for plain carbon steel. The protective layer develops and stabilizes after 6 to 24 months of natural exposure.
For high-humidity industrial settings—where airborne pollutants, moisture, and temperature cycling accelerate corrosion—Q355GNH offers 4 to 8 times the atmospheric corrosion resistance of ordinary carbon steel. This translates to a 35–50% reduction in surface maintenance costs over a 50-year service life, eliminating the need for repainting every 3–5 years required by conventional steels. The material is therefore widely specified for outdoor structures, bridge components, transmission towers, and containers in corrosive environments.
Just like you, 70% customers choose long-term cooperation with BBN steel not only for our good product and service quality, good reputation in the international market, but also for our experienced one-stop raw material supply and further steel processing!
