What is the function of sodium nitrate in a standard "recipe" for steam generator boilout compound?

Sodium nitrate serves several important functions in the context of a steam generator boilout compound, particularly in preventing caustic embrittlement. Caustic embrittlement occurs when concentrated caustic solutions thrive in the presence of certain steel types, leading to cracking and other forms of structural damage. Sodium nitrate helps mitigate this risk by creating a more stable environment within the boiler. It contributes to the thermal stability of the water and prevents the extreme local concentration of caustic soda, which can lead to embrittlement.

By maintaining a controlled concentration of alkalinity and enhancing the overall chemical balance during the boilout process, sodium nitrate aids in protecting not only the boiler components but also ensures the longevity and operational reliability of the steam generating equipment. This protective aspect is crucial in standard practices for maintaining steam generators.

Other functions mentioned, such as removing mill scale, preventing foaming, or protecting gauge glasses, may be relevant in other contexts or formulations, but the specific role of sodium nitrate in preventing caustic embrittlement is critical in ensuring the integrity of boiler materials during the boilout process.