The entire mooring complex was layed out on the decl< of a floating 

 crane (Figure 1 1) and later carefully lowered into service to avoid abrasion 

 or impact damage to the anodes. 



Immediately after placement of the mooring, the potential of the 

 buoy was found to be -920 mv. On the following day a potential profile was 

 made of the mooring, and the readings received are listed in Table 4. Another 

 potential profile was made 3 months later, after the chains had had considerable 

 time to erode the recently applied coal tar coating by movement during tidal 

 change. These later readings are listed in Table 5. 



The results of Tables 4 and 5 indicate that the zinc anodes were 

 working properly and that some of the ground tackle was being protected. 

 They also indicate that a lack of electrical continuity on other parts of the 

 ground legs prevented complete protection there. 



In order to determine ways to obtain better electrical continuity 

 between chain links, two of the ground legs were slightly modified 8 months 

 after the readings of Table 5 were made. One leg was removed from the water, 

 and those portions of the chain links that come into contact with each other 

 were sandblasted using the portable sandblast equipment aboard a floating 

 crane. This ground leg was then returned to its normal location underwater. 

 A second ground leg was removed from the water and layed out on the deck 

 of the floating crane. Three 3/4-inch-diameter galvanized steel cables were 

 woven back and forth through every sixth link. One cable extended from the 

 A-link nearest the anchor to the A-link nearest the zinc anode 45 feet away. 

 The other two cables extended between the zinc anodes which were 90 and 

 80 feet apart. The ends of each cable were silver-soldered to the A-link nearest 

 the anode (Figure 12), and the cable was also silver-soldered approximately 

 every 9 feet to the chain. Sufficient slack was allowed between fixed positions 

 so that there was no strain on the cable. This ground leg was then returned to 

 its normal position with no difficulty. 



While the ground legs were out of the water, each anode was examined. 

 There was no sign of passivation, and plenty of zinc remained for further use. 

 Zinc losses occurred in irregular pits rather than in a uniform manner. 



A potential profile was made on the entire mooring 1 week after the 

 two ground legs had been modified, and the readings are listed in Table 6. 

 They indicate that, while the sandblasting had little effect, the cables provided 

 the necessary continuity for complete cathodic protection. Because of the 

 very promising results with the cable-modified leg, the cathodic protection 

 design was further modified to include cables for all of the ground legs. 



17 



