Method used for bathycorrometer measurements: Prior to dive ops, instrument was turned on and suspended in seawater for about 30 minutes for equilibration. Soft and hard fouling growth was scraped away from metal surfaces (about a 2-inch diameter area) and black and grey oxide coatings over shiny metal were penetrated. Preliminary measurements had shown that readings made on black and grey oxides (presumably composed primarily of magnetite and hematite, respectively) were not consistently the same as readings made on shiny steel - thus all subsequent readings were made only on clean steel.

Measurements on the USS ARIZONA were made on: 1. vertical exterior hull surfaces, 2. superstructure surfaces, 3. a few hull surfaces beneath silt line, and 4. at and just below water surface at a few superstructure sites. Additionally, a few measurements were obtained from gunnel and superstructure locations on the USS UTAH in the course of one dive.

Control/drift check measurements were usually made on a gunnel site on the USS ARIZONA that was located about midship on port side. Drift was generally in the range of 0.002 volt over the course of a 1 to 2 hour dive.

Other notes: Fouling thickness measurements (in centimeters) include is total thickness of live and dead fouling. Dead fouling on most vertical surfaces averaged 1 to 2 cm thickness. Most of that material consisted of oyster and vermetid mollusk worm tubes that adhered tightly to the underlying oxide surfaces. Exfoliated = irregular oxide/steel plates delaminating from hull. Some exfoliated areas may actually be areas where a double hull exists with gaps of 1 to 5cm between plates. Areas of active corrosion, exfoliation and "delamination" were actually rare on the hull and superstructure surfaces deeper than 5 feet below surface.

Figure 4.13. Scott Henderson and another diver record bathycorrometer readings. (NPS photo by Larry Murphy)

VERTICAL STATIONS DATA

Note: Readings were made in closer area spacing on the forward port side of the USS ARIZONA. When it became evident that there was very little variation in readings, measurements were made only at tagged biological observations (numerical designation) stations.

SUPERSTRUCTURE STATIONS DATA

SUBSILT HULL DATA

Note: Holes were dug into silt adjacent to hull at four locations on both port and starboard sides. Holes were about 2.5 feet deep and hull at all subsilt locations was found to be covered with layer of dead, hard fouling. Depth of bathycorrometer reading (below silt surface) is given in notes column.

NEAR-SURFACE TRANSECT DATA

These measurements were performed on superstructure pieces that penetrated the water surface. B = water line, C = 1.5 foot below water line, D = 3 feet below water line.

MISCELLANEOUS BATHYCORROMETER READINGS FROM USS UTAH

25 July 1986 - R. Scott Henderson