What malfunction led to the steam leak on the USS Iwo Jima?

The steam leak on the USS Iwo Jima can be attributed to the replacement of the bonnet fasteners on the SSTG (Ship Service Turbine Generator) root valve with black oxide coated brass instead of the required carbon steel. This decision likely compromised the integrity of the valve assembly, leading to a steam leak.

Using the incorrect material for these fasteners would have affected their durability and ability to withstand the operating conditions associated with high-pressure steam systems. Brass may not have the same strength or resistance to thermal expansion and contraction as carbon steel, resulting in a failure point that could allow steam to escape. The specific material properties of black oxide coated brass can also contribute to issues such as galling or inadequate sealing, further exacerbating the risk of a leak.

In contrast, the other factors mentioned, while they can cause significant issues in a steam system, do not specifically align with the malfunction that resulted in the steam leak on the Iwo Jima.