EXAMINATION OF THE CORROSION AND SALT CONTAMINATION OF STRUCTURAL METAL FROM THE USS TECUMSEH
NAVAL RESEARCH LAB WASHINGTON DC
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The USS Tecumseh, sunk during the Civil War battle of Mobile Bay, is to be raised by the National Armed Forces Museum. Structural specimens were studied to determine the effectiveness of various methods of removing seawater salts from the corroded metal. The nature of the scale deposits and the extent of corrosion were also studied. With the exception of the rivets, the wrought iron of the hull was found to be in surprisingly good condition. The peened ends of the rivets had been deeply attacked, and cast iron deck plates had been perforated in places. Hull joints had been penetrated by corrosion and seawater. Ultrasonic cleaning was found to be ineffective in removing salts due to their encapsulation by the scale. Sandblasting to remove the scale, followed by flushing with water, appears to be the best cleaning technique. Analysis and examinations of the scale showed that there were typically 3 distinct layers, 2 of iron oxides and an exterior calcareous accretion. The formation of the scale layers can be explained by accepted corrosion mechanisms.
- Properties of Metals and Alloys
- Marine Engineering