Which chemical is commonly used to control alkalinity in boiler feedwater?

Caustic soda, or sodium hydroxide, is commonly used to control alkalinity in boiler feedwater. This chemical is effective at raising the pH level of the water, which helps to prevent the corrosion of metal components within the boiler system. Maintaining an appropriate level of alkalinity is critical as it helps to protect against harmful acidic conditions that can arise due to dissolved gases, such as carbon dioxide.

Using caustic soda in controlled amounts can enhance the formation of protective layers on the metal surfaces of the boiler, reducing the risk of pitting and other forms of corrosion. Furthermore, caustic soda acts to neutralize any acids present in the feedwater, making it an essential chemical in boiler water treatment processes.

In contrast, while other chemicals listed might have their roles in water treatment or other specific purposes, they do not serve the primary function of directly managing alkalinity in the way that caustic soda does in boiler feedwater.