Table 2. Potential Profile of Mooring With Zinc Anodes 







Potential (mv) on 









Reading 





















No." 



Riser-Chain 



Leg 1 



Leg 2 



Leg 3 



Leg 4 





(coated) 



(coated) 



(bare) 



(coated) 



(coated) 



1 



-830^' 



-750^ 



-770^^ 



-760^ 



-730"^ 



2 



-800 



-730 



-690 



-780 



-730 



3 



-800 



-700 



-690 



-700 



-670 



4 



-800 



-685 



-690 



-690 



-660 



5 



-800'^ 



-690 



-680 



-700 



-650 



6 



- 



-670 



-685 



-680 



-655 



7 



- 



-680 



-680 



-690 



-655 



8 



- 



-660 



-690 



-675 



-660 



9 



- 



-710 



-685 



-680 



-665 



10 



- 



-1 ,060*^ 



-885'' 



-890'' 



-840^ 



n 



- 



-710 



-670 



-690 



-685 



12 



- 



-715 



-680 



-700 



-710 



13 



- 



-735 



-690 



-810 



-730 



14 



- 



-775^ 



-SIO'^ 



-810*^ 



-730'^ 



" Readings taken approximately every 10 feet on the riser-chain and every 

 20 feet on the ground legs. 



^ At buoy. 



■^ At link to which remote ground cable is connected. 



At ground ring. 



^ At pipe on which anode was cast. 



Immediately after positioning the mooring, the buoy potential was 

 -740 mv. On the next day a potential profile was made of the mooring 

 complex, and the values received are listed in Table 3. They indicate that 

 more current was flowing because of the additional leads, but that the 

 ground legs were still receiving insufficient protection. The potential at 

 the anode pipe on Leg 1 had fallen to approximately the same level as that 

 on the other three legs, indicating that it was now functioning properly after 

 being repaired. 



The lower potential value on the buoy (-740 mv) after the addition 

 of the extra leads was attributed by the supplier of the zinc anodes to the 

 laying of a tighter mooring; this allowed greater amounts of current to flow 

 down the riser-chain, protecting the ground legs. In order to test this hypoth- 

 esis, potential values were measured down the riser-chain of another test buoy 



13 



