In the process of use, corrosion behavior is an important link that restricts the service life and safety of structural steel, among which atmospheric corrosion has a significant impact. To analyse the atmospheric corrosion behavior of structural steel in detail, accelerated corrosion experiments were conducted using a NaHSO3 solution to simulate industrial atmospheric conditions, and the corrosion behavior of the Q345B steel and weathering steel was studied. The weight loss due to corrosion was analysed, and the corrosion rate was calculated. After 168 h of corrosion, the weight loss rate of the Q345B steel is 2.25 g/(m2·h), whereas that of the weathering steel is only 1.74 g/(m2·h). Thus, the corrosion rate of the Q345B steel is higher than that of the weathering steel. X-ray diffraction analysis was used to determine the composition of the corrosion products. The primary corrosion products of both steels are identified as α-FeOOH, γ-FeOOH, Fe2O3,and Fe3O4.SEMobservations of the rust layer cross-sections reveal that initially, the rust layer of weathering steel is thin, approximately 41 μm, and grows slowly, whereas the rust layer of the Q345B steel is thicker, approximately 75 μm, and more porous. SEM analysis of the rust layers reveals that the base metal and corrosion products of the Q345B steel contain low levels of corrosion-resistant elements such as copper (Cu), chromium (Cr), and nickel (Ni), indicating no enrichment. In contrast, weathering steel contains detectable amounts of these elements, which are present to varying degrees. The enrichment of Cu, Cr, and Ni in the weathering steel rust layer effectively blocks the penetration of corrosive media, inhibiting the corrosion of the base metal. Therefore, weathering steel has better corrosion resistance than does Q345B steel.