and from their reports, they appear to be convinced that it furnishes 

 adequate protection against corrosion. These reports have mentioned actual 

 observations made "/hen the ships have been docked after the installation 

 has been in effect for some time. The Canadians are also trying this type 

 of protection on active operated ships as well as their inactive vessels. 



Some of the questions v/hich still remajn to be ans-rered on cathodic pro- 

 tection insofar as vre are concerned, are the following: 



A. .'hat is the effect of fouling upon cathodic protection? 

 >i'ill a cathodic protection installation on a badly fouled 

 hull protect that hull? It would seem reasonable to 

 suppose that heavily fouled hulls would retard or possibly 

 make non-effective the cathodic protection system, 



b. Over protection is harmful in that if too much current is 

 applied, the paint coating is adversely affected. Present 

 thought on the use of cathodic protection is that it would 

 be an adjunct to painting and if effective, ■'.'/ould lengthen 

 the time between dockings. It has not been considered a 

 complete substitute for painting. It is understood that 

 this is also the vier^TOint of the Bureau of Ships. It 

 could be that the Maritime Commission feels that they can- 

 not affort both docking for painting and cathodic protection 

 and therefore, are using the cathodic protection systems as 

 an alternative method for painting, 



c. From the Bxireau's experience and also from talking with 

 other people, it appeal's that cathodic protection is not 

 effective at the vfater-line area. Painting would, there- 

 fore, be required at this area whether or not cathodic 

 protection is used ani for an active operating dock, the 

 water-line area would extend from light draft without a 

 ship in dock to the pontoon deck level. 



From the Bureau's experience it is confidently believed that cathodic 

 protection has good possiPilities for the portion of the dock that is 

 alvjays under water but enough is not jet known about its effectiveness 

 to virarrant lOO/o reliance upon it and it is not felt personally that it 

 mil ever be the answer to all of exterior underwater corrosion problems. 



The deterioration of concrete structures offers soraeii/hat the same problems 

 as ?/ith steel structures in that there is sometlnes trouble v/ith structures 

 at or neai' the water front T/hich ar^ not submerged in sea water. The 

 reference here is to conditions such as recently experienced in Bermuda 

 and the .'est Indies in particular where serious concrete disintegration 

 problem.s occurred due to the direct action of salt v/ater v/hich it was 

 sometimes necessary to use in mixing concrete or to the action on the con- 

 crete of salt-laden spray. In both cases, the effect of the salt Y:ater 

 was aided and abetted in its action on the reinforcing steel and conduits 

 by the fact that available aggregates were somewhat porous in nature. 



D - 8 



