AbstractCorrosion affects the sustainability of steel structures, especially those with improper maintenance and those exposed directly to the atmosphere and seashore environments. Corrosion-related accidents have been reported frequently recently; therefore, periodically assessing the structural health condition of steel structures is crucial. Clarifying the residual strengths of corroded steel structures with moderate to severe degrees of corrosion is important. Here, the uniaxial compressive strength of corroded steel angles and channels was investigated through experiments and nonlinear finite-element analyses. The behavior of these corroded specimens was found to depend strongly on the degree of corrosion, and had combined failure modes of global flexural buckling, local buckling, and cross-sectional yielding. The failure mode of the corroded steel specimens that largely behaved in a complex manner was examined. The relationship between the ultimate strength and degree of corrosion, and the applicability of a traditional global flexural buckling strength equation using the cross-sectional properties, were analyzed for strength evaluation. The strength equation provided relatively good strength estimates for lightly to moderately corroded specimens; however, it became less applicable for severely corroded specimens, possibly owing to the local buckling interaction. An empirical strength equation that reflects the trend of the experimental results was developed by modifying the traditional equation.