in the San Diego Bay tlnat had a single zinc anode and a relatively slack 

 riser-chain. These values were found to be -980 mv on the buoy, -840 mv 

 4 feet down the chain, and -685 mv halfway down the chain. This indicates 

 that the fall-off in potential is more rapid for a relatively slack chain than for 

 a tighter chain. 



It was concluded that the zinc anodes were functioning properly, 

 but there were an insufficient number to produce the desired level of protec- 

 tion. Thus, the cathodic protection design was changed to include a greater 

 number of larger zinc anodes that would be cast on special chain links in 

 order to become an integral part of the ground tackle. 



Table 3. Potential Profile of Mooring With Zinc Anodes and Additional Leads 



Reading 





Potential (mv) on 



— 















No.'' 



Riser-Chain 



Leg 1 



Leg 2 



Leg 3 



Leg 4 





(coated) 



(coated) 



(bare) 



(coated) 



(coated) 



1 



-840^ 



-690'' 



-67 O'' 



-680'^ 



-690'^ 



2 



-850'' 



-640 



-655 



-655 



-640 



3 



-740'' 



-640 



-675 



-650 



-640 



4 



-720 



-635 



-675 



-655 



-635 



5 



-710 



-650 



-660 



-660 



-650 



6 



-690 



-640 



-660 



-645 



-640 



7 



-670"^ 



-655 



-655 



-640 



-675 



8 



- 



-675 



-660 



-650 



-680 



9 



- 



-700 



-695 



-660 



-700 



10 



- 



-710"^ 



-695'' 



-730'^ 



-710'^ 



11 



- 



-750^ 



-730'' 



-805*' 



-750'' 



12 



- 



-710^^ 



-700"^ 



-710' 



-710" 



13 



- 



-700 



-690 



-705 



-700 



14 



- 



-690 



-690 



-700 



-700 



15 



- 



-690 



-685 



-700 



-690 



16 



- 



-675 



-685 



-700 



-675 



17 



- 



-670'^ 



-695'^ 



-705'^ 



-670' 



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

 20 feet on the ground legs. 



At pipe on which anode was cast. 



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



'' At buoy. 



^ At ground leg. 



14 



