What is the desired value for pH in boiler feedwater?

The desired value for pH in boiler feedwater is typically between 8.5 and 9.5. Maintaining this pH level is crucial for several reasons. First, a higher pH helps to minimize the solubility of metals, particularly iron, which can corrode boiler components if left unchecked. By keeping the pH within this range, the formation of corrosion products such as magnetite (Fe3O4) is encouraged, which is a protective layer that can enhance the longevity and efficiency of the boiler.

Additionally, the pH range of 8.5 to 9.5 helps to facilitate the effectiveness of other water treatment chemicals, ensuring they function to remove impurities and prevent scaling and fouling within the boiler system. This level of pH also helps to reduce the risk of localized corrosion, particularly in areas where water may have a tendency to stagnate.

A pH below this range could lead to potential corrosion issues, while a pH that is too high can contribute to the formation of alkali deposits, which might negatively affect boiler performance. Thus, maintaining the pH in the range of 8.5 to 9.5 is essential for optimal operation and maintenance of boiler systems.