in shallow marine envirorjffl.ents is applicable with only slight modifications 

 to similar materials in a deep-ocean environment. For these reasons the 

 selection of materials for inclusion in the first phases of this program 

 has been limited to a representative sampling of varioiis material tjrpes 

 rather than directed toward the systematic coverage of each variety of 

 each type of material. However, through the cooperation of certain 

 industrial research laboratories j, a wide variety of small "screening 

 specimens" of various alloys has been included in the specimen load 

 of the first Submersible Test Unit (STU)= 



Although time=dependent changes in engineering properties of materials 

 may occur, chemical deterioration and corrosion are expected to be the 

 major processes of deterioration in the deep=ocean environment. For 

 piirposes of this report the term corrosion is defined as ".<., a gradual 

 chemical or electrochemical attack on a metal by its surroundings, such p 

 that the metal is converted into an oxide, salt or some other compound." 

 These major processes of deterioration will be influenced by the physical 

 environment (high hydrostatic pressure and low temperatxire ) and the 

 biological environments Since the rate and degree of deterioration are 

 also influenced by specimen configuration and by the mechanical and 

 physical struct-ixre of the metals, it will be necessary, in the case of 

 metallic specimens, to include variations in these factors as well as 

 variations in the alloying elements. 



The first materials to be extensively tested for suitability for 

 use in the deep=ocean environment will be those comm-only used in con= 

 ventional construction and available through normal supply channels. 

 If it is determined that these materials are not satisfactory for deep- 

 ocean structures^ then the less commcmlj used, exotic, and unusual materials 

 will also be studied. 



When constiiicting in a medium of relatively high density (compared 

 to air) such as sea water, there is immediately available a unique technique 

 of building virtually weightless structures and thus regulating the dead- 

 load pressure such a structure will exert on the ocean bottom. This 

 technique is based on the use of l«3w -density structural plastics, foamed 

 materials, and/or the incorporation of buoyancy through the use of either 

 voids or spaces filled with a buoyant fluid or other material. For this 

 reason, and also because of their resistance to sea-water corrosion, 

 plastic materials take on great importance. These include acrylics, 

 polyvinyl chlorides, polypropylene, polyethylene, polyeurthane, teflon, 

 nylon, rubber (both natural and synthetic), glass=fiber laminates, and 

 others. Samples of many of these materials will be included in this 

 program. 



Ceramic and glass materials are important to provide electrical 

 insxilation, view ports, and transparent closures for light sources, 

 cameras, and television; they are also used as structural elements in 

 some electrical lead -through systems. Some of these types of materials 

 will be tested. 



