The study reported in this paper was undertaken primarily for the purpose of developing failures in typical boiler plate under tension and in contact with high concentrations of sodium hydroxide in water solution. The failures occurring were examined carefully for evidence commonly considered indicative of caustic embrittlement. Photomicrographs are presented showing the presence of both intercrystalline and transcrystalline cracks. The author also includes a discussion of riveting pressures inasmuch as such pressures tend to affect the stresses in the fabricated unit. Impurites in the metal used for rivets and plates are also considered.

As a result of these studies it is concluded that whereas the stresses in the fabricated unit and the concentration of caustic in solution may be primary causes for the development of the phenomenon of caustic embrittlement, other factors contributing to metal stress and perfection of the fabricated unit may logically be considered in arriving at the fundamental cause of embrittlement. Typical of these factors are (a) riveting pressures, and (b) purity and uniformity of rivet and plate metal.

A more conscientious consideration of the nature of the resulting cracks in boiler failure will indicate the presence of both transcrystalline and intercrystalline cracks; and finally it is pointed out that intercrystalline cracks may not always be associated with caustic attack.

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