How do oxygen scavengers protect boiler systems from corrosion?

Oxygen scavengers protect boiler systems from corrosion by chemically reacting with and removing dissolved oxygen from the boiler water. Dissolved oxygen is a primary cause of corrosion in boiler systems because it promotes the oxidation of metal surfaces, leading to rust and other forms of corrosion. Oxygen scavengers are chemical additives that react with the dissolved oxygen to form harmless products, such as water and other non-corrosive compounds. Common oxygen scavengers include sulfite (SO32-), bisulfite (HSO3-), hydrazine (N2H4), and organic scavengers like diethylhydroxylamine (DEHA). For example, sulfite reacts with oxygen according to the equation: 2SO32- + O2 → 2SO42-. Hydrazine reacts with oxygen as follows: N2H4 + O2 → N2 + 2H2O. Organic scavengers typically react through more complex mechanisms to neutralize oxygen. The choice of oxygen scavenger depends on factors such as boiler operating pressure, temperature, and the presence of other chemical additives. It's important to maintain the correct dosage of oxygen scavenger to effectively remove dissolved oxygen without causing other problems, such as the formation of corrosive byproducts. Oxygen scavengers are often used in conjunction with mechanical deaeration to further reduce dissolved oxygen levels in boiler feedwater. Regular monitoring of dissolved oxygen levels and oxygen scavenger residuals ensures that the corrosion protection is effective.