Table 4. Performance of Systems I mmersed in Port Hueneme Harbor 







Time to Comparative 



Deterioration" After 





System 





Deterioration (yr) 



5 Years of Exposure 



Protection 

 Ranking 















Failure 



"9" Rusting"^ 



"M" Blistering'^ 



Rusting 



Blistering 





111 



>6.5 



>6.5 



>6.5 



10 



10 



-149 



112 



>6.5 



3.5 



>1.5 



9 



2D 



-94 



113 



>6.5 



>6.5 



>6.5 



10 



10 



-150 



114 



>7.5 



4 



>7.5 



9 



2F 



-105 



116 



>10 



5 



10 



9 



2F 



-120 



117 



>12.5 



9.5 



9.5 



10 



2F 



-155 



119 



>9.5 



>9.5 



>9.5 



10 



10 



-125 



120 



>12.5 



2.5 



>12.5 



9 



6D 



-145 



121 



>8 



5 



>8 



9 



2F 



-110 



122 



>5.5 



2 



4.5 



9 



6MD 



-85 



123 



9.5 



6 



>9.5 



9+ 



10 



95 



" ASTM rating. 



^ Protection ranking = approximately 10 times the years to failure (or estimated 

 failure if indicated by — ). 



"^ Time to reach an ASTM rusting rating of 9. 



Time to reach medium blister density according to ASTM rating. 



If the coating thickness is reduced by erosion, the resistance decreases 

 and the capacitance increases. If the coating thickness is reduced by distention 

 of the filnn, caused either by blistering or by rusting, the resistance is also 

 decreased and the capacitance is increased. Other defects or incipient breaks 

 in the coating will nnake more complicated changes in the effective electrical 

 network of the coating, but they will generally decrease the resistance and 

 increase the capacitance. Water uptake in the immersed film will increase the 

 dielectric constant and decrease the specific resistivity, and therefore, will 

 again have the effect of decreasing the resistance or increasing the capacitance. 



When electrical connections are made to the steel panel and to the 

 seawater in which it is immersed, the result is a parallel network consisting of 

 a capacitance and a high resistance. This network is in effect a nonideal capac- 

 itor as illustrated in Figure 23, The lower the resistance of this capacitor, the 

 greater is the loss current; and the greater the loss current, the greater is the 



32 



