What condition can occur in a boiler under stress with high alkalinity maintained?

Caustic embrittlement is a condition that can occur in a boiler when there is high alkalinity in the water, particularly when the pH levels rise significantly, usually due to the presence of sodium hydroxide or other similar compounds. This phenomenon is primarily linked to water treatment practices that inadvertently increase the concentration of hydroxides in the boiler water.

When high alkalinity is maintained, certain areas of the boiler, especially those that experience high temperatures and stresses (like welds or fabricated areas), can become susceptible to caustic embrittlement. This happens as alkaline conditions can lead to the formation of sodium carbonate or other caustic compounds that concentrate at metal surfaces. Over time, these compounds weaken the metal structure, particularly the stainless steel or low alloy steels commonly used in boiler construction.

The process is particularly dangerous because it can create micro-cracks in the metal, leading to sudden failure under stress. Therefore, proper water management and regular monitoring of alkalinity levels in a boiler system are essential to prevent caustic embrittlement and maintain the integrity of the boiler.