Structure and Formation Mechanism of Rust Scales on 09CuPCrNi Weathering Steel in Wet-dry Cyclic Corrosion

The rust scales on 09CuPCrNi weathering steel after accelerated wet-dry cyclic corrosion tests were investigated in order to realize the mechanism of the formed rusts. The rust scales were composed of a dense inner layer and a loose outer layer. The inner layer grew thicker and denser with the test period increasing. Large amount of γ-Fe2O3 was detected in the inner layer, which might be the reason resulting in much denser inner layer. Easy formation of γ-Fe2O3 may be attributed to the alloying elements of copper, chromium and phosphorus enriched in the inner layer.