Table 1. Potential Profile of IVlooring With Magnesium Anodes 







Potential (mv) on- 









Reading 





















No." 



Riser-Chain 



Leg 1 



Leg 2 



Leg 3 



Leg 4 





(coated) 



(coated) 



(bare) 



(coated) 



(coated) 



1 



-730* 



-700^^ 



-700^^ 



-700' 



-700' 



2 



-710 



-700^^ 



-710"^ 



-720"^ 



-690^ 



3 



-710 



-670 



-710 



-710 



-700 



4 



-710 



-680 



-710 



-720 



-700 



5 



-700' 



-670 



-710 



-710 



-710 



6 



- 



-670 



-700 



-700 



-670 



7 



- 



-670 



-690 



-700 



-660 



8 



- 



-670 



-700 



-700 



-660 



9 



- 



-710 



-680 



-700 



-670 



10 



- 



-710 



-690 



-700 



-700 



11 



- 



-710 



-710 



-710 



-695 



12 



- 



-710 



-730 



-720 



-680 



13 



- 



-720'' 



-730'^ 



-710'^ 



-670^^ 



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

 20 feet on the ground legs. 



* At buoy. 



'• At ground ring. 



At link to which remote ground cable is connected. 



Zinc Anodes 



Installation of Zinc Anodes. At the time the magnesium anodes were 

 to be replaced with ones of zinc, the buoy potential was -730 mv, the same 

 as when measured 3 weel<s earlier. The buoy was lifted out of the water onto 

 the deci< of a floating crane. There was considerable fouling, notably tunicates, 

 on both the buoy and the two magnesium anodes. The square of bare steel in 

 the submerged zone of the buoy had a light coat of rust that was easily removed 

 by manual wire brushing. 



The magnesium anodes were removed from the buoy with no difficulty 

 because the nuts and studs securing them had very little corrosion. Zinc anodes, 

 each weighing 144 pounds, were installed where the two magnesium anodes had 

 been removed. The remote ground cable was severed at each control head, and 

 two inches of insulation were cut from the ends. The bare ends were placed 



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