From 1960 to 1975, the U.S. Navy performed a pioneering effort to determine the effect of deep ocean environments on materials, in this program, seven large sample racks were exposed to the deep ocean environment and, for comparison purposes, samples were also exposed to surface seawater. The deep water exposures were at nominal depths of 760 M and 1825 M for periods of up to three years. Over 20,000 specimens of 475 different alloys were exposed and evaluated in the program.
This paper outlines the methods used to prepare, expose and evaluate the samples and gives a brief overview of the results of the effort.
The results of the effort demonstrated that, for some materials, there was a significant difference in their behavior in deep water compared to their performance in surface waters. In some cases, corrosion in deep water was more severe than in near-surface waters. In other cases, corrosion in deep water was less severe than in near-surface waters. For some materials, there was little difference between corrosion in deep water and in surface water. Biofouling was present in the deep water exposures, but the amount of biofouling was much less than in near-surface waters.
In the early 1960's, the U.S. Navy was investigating the placement of permanent facilities in the deep ocean for military purposes. As these were to be fixed facilities, the Naval Facilities Engineering Command was responsible for the design, construction, operation and maintenance of these facilities.
In the 1960's, the long term performance of materials in deep ocean environments was essentially unknown. The only information on the performance of materials in deep ocean environments was from observations of instruments or other objects that had been exposed to deep ocean environments, usually for short periods under uncontrolled conditions and without quantitative measurement of the corrosion that occurred.
In the early 1960's the Naval Civil Engineering Laboratory, now the Naval Facilities Engineering Service Center, was tasked with developing and executing a program to determine the performance of materials in deep ocean environments.
In this program, a total of seven Submersible Test Units (STU's) were exposed at nominal depths of 670 M and 1825 M for periods ranging from 123 days to 1064 days. Over 20,000 specimens of over 475 different metals and alloys were exposed in the program. The STU's were emplaced and retrieved using several different types of Navy vessels ranging from landing craft- tank (LCT) with land based cranes lashed to their well decks to fleet salvage tugs (ARS).
In 1982 the United Nations adopted the Convention on the Law of the Sea which prohibited the use of the seabed for military basing. Although this reduced the funding available for additional deep ocean corrosion exposures, the data obtained from the deep ocean and near-surface corrosion testing was considered to be sufficiently valuable to complete the analysis of the data and publish the data for public release. Some specific deep ocean testing for the development of seals and gaskets for deep ocean applications such as manned submersibles and in support of specific programs such as the Deep Submergence Rescue Vehicle (DSRV) continued into the 1980's.