Chapter IV: Biofouling And Corrosion Study
(continued)

Corrosion and Steel Fabric Thickness Study

Methods

Twelve stations were selected on hull and superstructure surfaces that had access to metal edges (Figure 4.8). At each station, divers used a claw hammer to chip away a few square inches of fouling growth and corrosion from both sides of the metal edge to expose shiny metal. Observations were then made of the thicknesses of dense fouling, black and grey oxides, and shiny steel that were visible in the exposed end sections.

Figure 4.8. Locations where measurements were made of thickness of corrosion products and underlying shiny steel on edge sections of hull and superstructure fabric on the USS ARIZONA.

These measurements were made in order to permit future corrosion engineers to estimate corrosion rates at those locations. Metal thicknesses of the steel fabric at the specific locations will have to be obtained from drawings/specifications of the ship that show its condition immediately prior to 1945. Those thicknesses can then be compared to the thicknesses obtained in later observations to estimate the amount of steel loss that has occurred.

It is recognized that surfaces on or near exposed edges might be affected by edge events that could alter measurements of corrosion, in other words, yielding higher corrosion rates than would occur on large-area flat surfaces. However, since sampling removal of metal pieces from flat areas was not allowed, it was decided to examine the edge corrosion to allow at least a worst-case estimation of corrosion rates.

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