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Let’s discuss the factors by which petrochemical wastewater corrodes concrete structures. Due to the complex composition of sulfur- and alkali-containing wastewater (hereinafter referred to as sulfur-containing wastewater), which contains many harmful substances, it causes severe corrosion to concrete tanks that are in use over a long period of time. The cause of corrosion on the concrete surface is the damage to the protective coating, which allows sewage to directly erode the concrete surface; sulfur-containing sewage contains large amounts of sulfides as well as light oils. Among them, sulfides generally exist in the form of sodium salts (NaH2S, NaS), ammonium salts such as NH4HS and (NH4)2S, as well as thiol organic compounds. When sulfides come into contact with oxygen in the air, an oxidation reaction occurs; sodium salts and ammonium salts are oxidized to thiosulfates, and then a small portion (10%) of these thiosulfates is further oxidized to sulfates. The presence of these acidic impurities causes severe corrosion of concrete. The main factors causing corrosion damage to concrete are as follows. 1. Colloid dissolution: When wastewater comes into contact with the concrete on the inner walls, it causes the colloids present in the concrete to dissolve. First, calcium hydroxide is dissolved and carried away, resulting in cracks; as a result, the concrete’s water resistance gradually decreases until it eventually gets damaged. 2. Crystal expansion: Due to the erosion by wastewater, chemical reactions occur within the cement paste and aggregates in concrete. Some of the products of these reactions dissolve in water, while other crystalline substances gradually fill the pores where they are formed, continuing to grow and causing stress on the inner walls of those pores, which leads to rapid cracking of the concrete. 3. Expansion of rust deposits: In a state of water saturation, the concrete cover may be thin, but due to corrosion, its surface peels off in patches. The corrosive water comes into contact with the rebar, triggering an electrochemical reaction that results in the formation of large amounts of rust. The volume of rust keeps increasing (by about 2-3 times), causing the concrete to swell continuously, and as a result the degree of damage to the concrete becomes more severe. 4. Effect of temperature: The gradient caused by the temperature difference between inside and outside the pool exacerbates the freeze-thaw damage to concrete. When the temperature of the pool walls is lower than the internal temperature, according to the principles of thermodynamic equilibrium, the water with higher free energy within the concrete causes the volume of water crystals to increase. The growth of these ice crystals damages the structural organization of the concrete. The above factors interact and accumulate with one another, causing the corrosion rate to increase significantly and the degree of damage to become markedly severe.