Revealing the corrosion resistance mechanism of ultrahigh-strength titanium microalloyed weathering steel

This study used cyclic immersion tests and electrochemical techniques, along with various characterization methods, to compare the corrosion resistance of 2.2Cr and 3Cr titanium microalloyed weathering steels and investigate the corrosion resistance mechanisms of ultrahigh-strength titanium microalloyed weathering steel. The results show that the 3Cr titanium microalloyed weathering steel exhibits the best corrosion resistance. The rust layer of 3Cr titanium microalloyed weathering steel forms a three-tier protective system of “external barrier-intermediate buffer-internal dense layer” effectively enhancing the corrosion resistance of the test steels. The outer rust layer is mainly composed of Fe 3 O 4 and γ-FeOOH, but FeCr 2 O 4 and α-(Fe, Cr)OOH rich in Cr can physically adsorb water molecules, O 2 , and HSO- 3/SO2- 4, thereby delaying the diffusion of the medium. The intermediate rust layer has a multi-layered structure with diverse synergistic effects, resembling a bionic shell, which can dissipate stress through cation selectivity and micro-crack tortuosity. The inner rust layer primarily contains α-FeOOH/α-(Fe, Cr)OOH and Fe 3 O 4 /FeCr 2 O 4 , with minor MnFe 2 O 4 , CuFeO 2 , and amorphous δ-(Fe, Cr)OOH. The stable and dense inner rust layer acts as the final barrier, effectively blocking the intrusion of corrosive media.