Monday, August 18, 2014

Preserving our Past: HRNM's Anchor, Part 2 of 2

The modern-day journey for one of HRNM’s largest artifacts, a 200-year-old anchor, began in 1993 (read part 1 about the anchor here). In order to treat the anchor and preserve it for the future, Dr. Brad Rodgers of East Carolina University constructed a preservation tank in November 1993. His team built the tank by digging a hole, lining it with cinder blocks, and then pouring concrete to create the tank’s walls. They built an I-beam superstructure over the tank that would allow them to raise and lower the anchor as well as turn it over. The tank held 4,000 gallons of water and was fourteen feet long, nine feet wide, and four-and-a-half feet deep.
The anchor being delivered to HRNM after preservation was completed.
Throughout the process the conservation tank was filled with either distilled water or rainwater. Once the anchor was submerged in this water, conservationists added sodium carbonate and placed steel anodes over the shank and arms of the anchor. The anodes did not make contact with the anchor, but formed a tent-like structure over it instead. An electrical current then ran through the anodes. This complicated procedure allowed the corrosion on the anchor to change from its original state into magnetite or hematite, which reduced the thickness of the corrosion and allowed chlorides to rinse out of the anchor. Conservationists emptied the tank halfway and refilled it with fresh rain or distilled water several times throughout the process. This was continued until all of the salt was removed from the anchor.

Dr. Rodgers estimated that five percent of the anchor’s weight, or sixty pounds, was salt. After the anchor was preserved, it was painted with several protective coatings. On average, the preservation process takes four to six years, but a number of hurricanes delayed the process. In 1999, Hurricane Floyd’s rains contaminated the tank with mud and other debris. After the hurricane Dr. Rodgers and his team decontaminated the tank and re-started the process from the beginning. It was not until December 2005 that the anchor’s preservation was finally completed, and it is now on display at the Naval Museum.

(This blog post was written by HRNM Public Relations Coordinator Susanne Greene.)

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