Abstract: The effect of nickel on the ion-selective property of the rust layers formed on the low alloy weathering steels under marine atmosphere was investigated by an alternate wet-dry accelerated corrosion test. Four types of low-alloying steels with different Ni contents were prepared for the corrosion test. The rust formed at various stages of corrosion was characterized by electrochemical impedance spectra (EIS), electron microprobe analysis (EMPA) and scanning electron microscopy (SEM). Afterwards, the corrosion resistance property of the rust was studied in the light of the experimental results. It is shown that increasing Ni content has significantly improved the corrosion resistance of the low-alloying steels under marine atmosphere. Furthermore, it is noted that an evident cation-selective property emerges in the rust layers with the Ni content of the rust layers up to 1.82%. However, when the Ni content of steel the matrix is below 1.5%, it has little effect on the cation-selective property. The ratio of Ni content in between the rust layer and the steel substrate decreases with the increase of Ni content in the steel substrate and varies little as the corrosion proceeds.

Key words: Atmospheric corrosion, Nickel oxide, EIS, SEM