INTRODUCTION 



Anaerobic environments are usually found in the oceans wherever 

 circulation of oxygenated seawater is restricted or where decaying 

 organic matter is discharged. Anaerobic ocean areas frequently occur in 

 harbors and bays and adjacent sewage outfalls. 



In an anaerobic marine environment, hydrogen sulfide is always 

 liberated. As long as free oxygen is present, marine bacteria utilize 

 it to oxidize organic matter. In the absence of free oxygen, the bac- 

 teria oxidize their food by reducing sulfate ions in the seawater, and 

 hydrogen sulfide is evolved in the process. 



Hydrogen sulfide greatly accelerates the corrosion of iron and 

 steel [1]. It is reported [2, 3] that iron and steel pipes, pumps, 

 storage tanks, piling, mooring chains, ship hulls, and painted metal 

 surfaces corrode rapidly in an anaerobic environment where copious 

 quantities of hydrogen sulfide are present. 



Tests were undertaken at the Civil Engineering Laboratory (CEL) to 

 ascertain if structural plastics and other polymeric materials also 

 undergo rapid deterioration in an anaerobic environment. This report 

 describes the CEL tests in which specimens of a wide variety of plastic 

 sheeting, electrical cable insulation, and synthetic fiber ropes were 

 exposed to an anaerobic marine environment for 2-1/2 years. For compari- 

 son, natural fiber ropes, wood, and rubber were also subjected to the 

 same environment. For further comparison, all of the materials were 

 also placed in aerobic, near-surface waters. 



MATERIALS AND METHODS 



Test Specimens 



Several 6- by 12-inch panels were cut from sheets of the plastic 

 materials listed in Table 1 . The sheets of polytetraf luoroethylene and 

 polyurethane were each 1/16 inch thick; all of the other sheets were 1/8 

 inch thick. Rope specimens approximately 2 feet in length with eye- 

 splices formed at each end were prepared from each of the materials 

 listed in Table 2. The diameter of the cotton ropes was 1/2 inch, and 

 the diameter of all the others was 1/4 inch. Ten-inch lengths of insu- 

 lated electrical cable covered with the materials designated in Figure 1 

 were mounted on plastic panels having dimensions of 1 /8 by 6 by 12 

 inches. Panels of Douglas fir measuring 1/4 by 6 by 12 inches were also 

 prepared for the tests. 



