Role of Cr in the Anticorrosion Ability of Weathering Steel Based on the Microcharacteristics of Synthetic α -FeOOH in the Presence of Cr(III)

The effect of Cr on the corrosion behavior of weathering steel (WS) in a simulated industrial atmosphere has been clarified by determining the microcharacteristics of artificially synthesized α -FeOOH in the presence of Cr(III). WS showed higher corrosion resistance with increasing Cr content, and the effect became more obvious with prolonged corrosion time, which is because Cr addition helps form more compact rust layers and produces high contents of α -FeOOH and α -Fe x Cr 1− x OOH in the corrosion scales. Aging experiments showed that adding Cr(III) can enhance the compactness of corrosion scale via two mechanisms. Increased addition of Cr(III) can form schwertmannite as a precursor for α -FeOOH, which promotes the formation of α -FeOOH and increases its content in corrosion products. On the other hand, increased addition of Cr(III) can decrease the grain size of α -FeOOH and schwertmannite. Furthermore, Cr(III) can replace edge-shared Fe(III) octahedra in double-chain α -FeOOH to form α -Fe x Cr 1− x OOH in stable rust layers. These results further elucidate the function of Cr in the anticorrosion ability of WS in an industrial atmosphere.