<p>Corrosion resistance is an important indicator in determining the service life of low-carbon steels. The Sb element microalloying method was used to optimize the corrosion resistance of low-carbon steel in the present study. The results showed that the minor addition of Sb element does not change the original microstructure of ferrite and pearlite in low-carbon steel. However, the alternate immersion corrosion performance in the simulated coal solution was significantly improved with the addition of Sb element. The rust layer of Sb-contained steel (SB steel) immersed in the coal solution for 20 d possessed superior electrochemical performance than that of low-carbon steel without Sb element (BS steel). The rust layer became dense correspondingly with the immersion period due to the formation of α-FeOOH caused by the enrichment of Sb and Cr in the inner rust layer. Thus, the densification and stability of rust layer were improved. In addition, the bonding force between rust layer and substrate was improved. The stable rust layer in SB steel enhanced the resistance to corrosive ions, such as Cl^- and SO₄^2-, and thus improved corrosion resistance of low-carbon steel.</p>