When adopting new equipment, it must be compatible with the production process to avoid unnecessary corrosion-related losses

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When adopting new equipment, it must be compatible with the production process in order to avoid unnecessary corrosion-related losses. Example: The LSB type submersible pump for high-temperature concentrated sulfuric acid is a new type of circulation acid pump that has been successfully used in sulfuric acid production plants. However, in two sulfuric acid plants, the pumps had been in operation for only 2 months when it was found that the pump bodies made of alloy cast iron, along with the inlet and outlet acid pipes, were severely corroded, and the pump bodies had developed holes. Sulfuric acid concentration: 97–98%, temperature: 75–85°C. In other plants, the temperature can exceed 90°C, or the acid concentration can be below 90%, yet no problems have occurred over several years. Analysis: Upon examination, it is found that these two plants use a hot concentrated acid washing process (while other plants use water washing or closed-loop acid washing), which results in a high level of impurities in the acid used in the absorption cycle. Compounds such as Cu2+, AsO43+, Fe3+, and SeO42- are all strong oxidizing agents. Alloy cast iron parts cannot form a passivation film under such operating conditions, thereby accelerating corrosion. Improvement measures: To address the corrosion issue of the pump, it is possible to start with the manufacturing process by reforming the pickling procedure. Otherwise, materials with better corrosion resistance, such as Alloy 3, must be used. Alloy 3 has a strong passivation ability in hot concentrated sulfuric acid (it can be fully passivated even at 90°C), and these oxidizing impurity ions can actually promote passivation.