Abstract: The material of center cylinder rib plate of sulfuric acid converter underwent severe oxidation and material degradation. The reasons for the deterioration of the rib plate were analyzed using macroscopic observation, chemical composition analysis, mechanical property testing, metallographic examination, scanning electron microscopy and energy spectrum analysis, X-ray diffraction analysis. The results show that the carbon element content of the rib plate was slightly higher, the Cr element content was lower, and the Ni element content was lower than the standard requirements, resulted in a decrease in the plasticity of the material. The use temperature of the rib plate was relatively high, reached the lower limit of the flue gas corrosion temperature, which promoted the oxidation corrosion of the rib plate. The microstructure of the rib plate mainly contained austenite and σ precipitates, with widened grain boundaries, ultimately led to the transformation of the material into strong brittleness and deterioration.