In a caustic storage vessel, where is caustic embrittlement least likely to occur?

Caustic embrittlement is a phenomenon that occurs primarily in carbon steel vessels when exposed to a caustic environment, generally leading to hydrogen embrittlement. This issue is more likely to arise in areas of the vessel that experience high stresses and in places where the caustic solution may accumulate or be turbulent.

In the context of a caustic storage vessel, the regions near the internal baffles or vortex breakers typically experience better mixing and reduced stagnation of the caustic solution. This means there is less buildup of concentrated caustic, which reduces the likelihood of embrittlement occurring. Additionally, these areas tend to have lower stress conditions compared to seams and high-stress areas, further decreasing the risk of localized failure.

By contrast, seams in the structure are stress concentrators and have the potential for imperfections that may be exacerbated in a caustic environment. High-stress regions are also more susceptible to embrittlement due to the combination of stress and chemical attack. The bottom of the vessel might have caustic accumulation, leading to a higher risk of embrittlement than the area near baffles, especially if the vessel is not emptied regularly.

Thus, the area around internal baffles or vortex breakers is indeed