electrometer 



panel 



A \ S^ • 



± 



Figure 22. DC source for impressed potentials. 



The logarithms of the DC resistance measurements are also shown in 

 Table 2. The initial values were obtained after approximately 1 hour; the 

 1 0-day values indicated were obtained after approximately 7 to 1 days. 

 Average values are shown; panels for which log R would have deviated by 

 more than 0.5 from the averages were not included in the averages. The changes 

 in log R are also shown. 



The panels were rated visually after 2, 5, 1 3, and 22 months for rusting 

 and blistering.''^ The rusting ratings were assigned according to ASTM method 

 D G 10-43, in which a rating of 10 designates no rusting and lower numbers 

 designate increasing rusting. The blistering ratings were assigned according to 

 ASTM method D 714-56, in which a rating of 10 designates no blistering and 

 decreasing numbers indicate increasing blister size, and in which the letters 

 F (few), M (medium), and D (dense) indicate increasing blister density. 



Before these ratings, and at other times when the buildup of organic 

 debris or the brown coloration on the panels appeared excessive, the panels were 

 removed from the aerated seawater and were cleaned with a soft brush. They 

 were rinsed with seawater and briefly with demineralized water before being 

 replaced in fresh seawater. 



29 



