Impact of cerium on microstructure of rust and corrosion resistance of Cu-Cr-Ni-V micro-alloyed steels in NaHSO₃ acid accelerated test

Corrosion resistance, microstructure and corrosion products of rust and inclusions of Cu-Cr-Ni-V micro-alloyed steels containing 0.0015% cerium (Ce) were investigated by NaHSO 3 acid-accelerated test. The results revealed the presence of three-layer microstructures in rust: bottom layer (Fe 3 O 4 ), interface layer(α-FeOOH) and cracks layer(α-Fe 2 O 3 ) from inner to outside. The introduction of cerium facilitated the formation of α-FeOOH and Fe 3 O 4 in the rust, while reducing the prevalence of α-Fe 2 O 3 in the rust. The type of inclusions transitioned from undissolved inclusions to dissolved Ce-based inclusions in the acid solution and corrosion rate was reduced by 27% by adding the Ce to the micro-alloyed steels.