Corrosion failure analysis of a railway tanker containing concentrated sulfuric acid

Abstract

In this paper, the authors carried out a corrosion failure analysis of a railway tanker containing 92.5% sulfuric acid, in order to investigate the cause of the leakage accident that occurred in 2016 and to provide a theoretical basis for preventing similar accidents. The morphology and chemical composition of the corrosion scale were characterized by SEM and EDS. The theoretical corrosion rate of the railway tanker was calculated using weight loss experiments. The corrosion behavior model was established by electrochemical experiments. In order to investigate the cause of this leakage, a mechanical model was established, and the force of the railway tanker during transportation was analyzed through ANSYS software. The results show that the tanker material (low-alloy high-tensile structural steel, Q295A) meets the quality standard, and the main cause of this leakage accident was the local corrosion failure of the tanker leading to a crack due to stress during the transportation process. The corrosion source is diluted H2SO4 solution. The main component of the corrosion scale was Fe2O3. The theoretical corrosion rate was in the range of 1.413–1.978 mm/a, and the corrosion rate increased with the decrease in the concentration of H2SO4. The corrosion type was pitting corrosion. When the brake is applied when the tanker is in full load, the stress inside the tanker is about 8.94 times higher compared to a tanker with empty load in the static state. Because of this uneven force, a crack may develop leading to leakage from the corroded area of the tanker.