Where is caustic embrittlement most likely to occur?

Caustic embrittlement is a form of corrosion that occurs primarily in steel and iron under specific conditions, particularly where high concentrations of hydroxide ions (alkaline conditions) exist. This phenomenon is most likely to occur in riveted joints situated below the water line due to the combination of moisture and the presence of dissolved alkalis, which can create corrosive environments that promote embrittlement.

In riveted joints, especially those submerged in water or subject to moisture, the alkaline conditions can arise from the chemical interactions in the water, particularly if sodium hydroxide (or caustic soda) is present. This leads to the breakdown of the metal's properties, making it susceptible to mechanical failure.

The other scenarios, such as welded joints above the water line or stainless steel piping systems, do not create the same conducive environment for caustic embrittlement. Welded joints can generally provide better resistance due to the nature of the weld itself, and stainless steel is less prone to caustic embrittlement due to its passivation properties and resistance to corrosive environments. Exposed fittings above ground are also less likely to experience the conditions necessary for caustic embrittlement, primarily due to lack of moisture and the presence of atmospheric conditions