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The main reason for the reddening of water in drum boilers is excessive iron ions, which indicates that corrosion is occurring within the boiler system. It is necessary to investigate and address this issue promptly to avoid potential safety hazards. I. Main causes: System metal corrosion. Oxygen and carbon dioxide dissolve in water to create an acidic environment, which destroys the passivation layer on the pipe walls. This leads to the formation of corrosive products such as red iron oxide and ferric oxide; when these substances mix with the boiler water, it causes the water to turn red. Invasion by external impurities: Excess iron content in the feed water and condensate, or failures in water treatment equipment and pipe corrosion, can introduce iron ions into the furnace ； As the boiler water continues to evaporate and concentrate, ferrous iron is oxidized to colored ferric iron, causing the color to deepen continuously. Improper operation led to insufficient dosing, which prevented the maintenance of a normal pH level (standard range: 9.0–10.5). Inadequate waste removal caused impurities to accumulate inside the furnace ； Failure to carry out passivation during the startup and shutdown phases of the boiler, as well as significant fluctuations in operating conditions that lead to stress corrosion, can all exacerbate the red water phenomenon. II. Control and Treatment Measures: Conduct rapid investigation and identification by testing parameters such as the iron content in the boiler water (which should be below 0.1 mg/L), pH value, and dissolved oxygen; also check whether there are any leaks or malfunctions in equipment such as deaerators and condensers. Adjust the operating parameters by increasing the frequency of continuous and periodic slag discharge to remove the iron impurities accumulated inside the furnace ； Adjust the dosage of chemicals to maintain the pH value of the boiler water at around 9, thereby slowing down the corrosion process. Root cause anti-corrosion treatment: optimize the operating conditions of the deaerator to reduce dissolved oxygen in the feedwater ； Applying appropriate corrosion inhibitors forms a protective film on the metal surface, preventing corrosion caused by oxygen and carbon dioxide, and reducing the formation of iron ions at the source.