The function of Cr on the rust formed on weathering steel performed in a simulated tropical marine atmosphere environment

The atmospheric corrosion behavior of weathering steels (WSs) with dissimilar Cr contents was studied through dry/wet cycling corrosion tests combined with electrochemical measurements and characterizations of morphology and composition of the rusts. The results presented that the corrosion rates of WSs decreased as the Cr contents in WSs increased, which manifested as an increase in the impedance for rust layers after various corrosion periods. The enriched area of Cr in the inner rust layer was more evident in blocking the invasion of Cl-, which is related to the positive ion selectivity of the rust. High content of Cr in steel promotes the generation of Cr(OH)3 and Cr2O3, which acted as nucleation sites for the formation of Fe3O4 and α-FeOOH, presenting high value of α*/γ (the sum of α-FeOOH and Fe3O4 / γ-Fe2O3 to γ-FeOOH).