Su I fate-reducing bacteria were found to be responsible for a severe external 

 anaerobic corrosion of a ship's hull which laid on mud banks of a river estuary for 

 several months after launching. Pitting and black corrosion products were observed 

 on rivet points and plates. The liquid extracted from inside the paint blisters on the 

 ship's hull have been reported to contain sulfate-reducers, and their deleterious 

 action is considered to be more widespread in marine corrosion than has been previously 

 suspected. 26 Anaerobic corrosion is one of the several important types of corrosion 

 v/hich cause metal loss estimated at between 5 and 6 billion dollars annually in the 

 United States. 27 |n studies 28 wherein steel test samples were immersed in sterile 

 sea water (bacteria-free) for 6 months, the corrosion rate was 0.0294, 0.0397, and 

 0.066 gram per square meter per hour; however, samples of steel exposed to the 

 action of natural marine bacterial populations in the North Sea showed a 20 to 

 25 percent increase in the deterioration rates. This increase was attributed to 

 increased acidity of the liquid medium and changed electric potential of the metal 

 due to the metabolic activity of marine bacteria. It was demonstrated that micro- 

 organisms isolated from corroding steel samples attacked newly submerged steel 

 samples more aggressively than those bacteria normally found in sea water. 



Concrete sewer pipes and buried iron conduits are severely damaged by sulfur 

 bacteria (genus Thiobacillus ). These bacteria utilize elemental sulfur, thiosulfates, 

 and hydrogen sulfide as sources of hydrogen or energy, oxidizing these substances 

 eventually to sulfuric acid. The acid attacks concrete and iron conduits, causing 

 severe deterioration. 



Fish, Sharks, and Sea Urchins 



Certain varieties of marine fish are attracted to white polyethylene-covered 

 cables and lines. Nibbling by these fish has caused considerable damage to 

 insulations. It is suggested 2" that the use of black polyetheylene-covered cables 

 in the sea is advantageous since they do not attract fish. There is a report about 

 sharks which like to test their teeth and jaws on submarine cable sheathings, often 

 leaving their teeth embedded clear through the copper core. 



The purple sea urchins, Strongylocentrotus purpuratus , were blamed for the 

 destruction of steel H-beam piles in 30 feet of water about 1,500 feet from shore. 

 Of the 42 steel piles (oil-well pier) pulled, about half were damaged by these 

 urchins. The abrasive action of the sea urchins kept the rust cleared, leaving the 

 bare metal continuously exposed to the corroding action of sea water. The adjoining 

 pits made by the urchins became large holes; as these holes merged, the damaged 

 isolated sections of the steel piling finally fell before the forces of the surging sea. 



10 



