The capacitance-measuring assembly provided series capacitance and 

 dissipation factor readings and also parallel capacitance and conductance. The 

 resistance values were calculated from the conductance values. The measure- 

 ments were made with three-terminal connection to the capacitance bridge. 

 A lead with grounded shield was attached by an insulated alligator clip to the 

 handle of the panel being measured and contact with the seawater was main- 

 tained through a cylindrical platinum screen electrode 15 mm in diameter and 

 50 mm high. The connection from the capacitance bridge to this electrode 

 also had a grounded shield. Measurement errors with this assembly were 

 negligible, even at frequencies up to 10 Hertz. 



The capacitance and dissipation factor measurements and the conductance 

 measurements were made as frequently as possible immediately after exposure 

 and during the first day of exposure; they were then made less frequently as the 

 exposure continued. The average values obtained for the three panels are plotted 

 in Figures 3 to 15. The average initial values are indicated at the left-hand ordi- 

 nate scale of the curves. The first measurement that was made after an initial 

 24-hour period and further measurements up to 400 days are shown in the 

 curve. Where the measurements for some panels deviated considerably from the 

 average value, these values are indicated at the right-hand ordinate. 



Some of the electrical properties are also shown in numerical form in 

 Table 2. The values listed are the initial values, the values after 6 hours, and 

 the values after 10 days, 150 days, and 400 days (or approximately 1 year). 

 The values shown are the averages of the better panels. Values which were 

 considerably inferior to the averages (that is, low resistance values and high 

 capacitance or dissipation factor values) were not included in the averages, as 

 discussed below. In addition to the resistance and capacitance values at the 

 particular exposure times, the ratios representing the changes from the original 

 values, and also the logarithms of these ratios are shown. 



The AC resistance, capacitance, and dissipation factor values obtained 

 during the first 6-hour immersion period and during the first 10-day immersion 

 period were also separately plotted for each system. The curves obtained for 

 the four systems having the most significant changes are shown in Figures 16 

 to 19. 



After approximately 3 hours, and again after approximately 2 weeks, 

 the dissipation factors at different frequencies from 200 Hertz to 10 kHz were 

 also determined for each system. The curves for the 14-day values for 12 of 

 the systems are shown in Figures 20 and 21. Also shown is a plot of the 2-hour 

 values for one of the systems. 



DC electrical measurements were made by a modification''^ of the 

 methods of Bacon^ and of Brown. ^ Contact to the seawater was maintained 

 with a calomel electrode, and voltage measurements were made for the voltaic 

 cell: panel/coating system/seawater/calomel electrode. An electrometer with 

 an input resistance of 10''^ ohms was used (Keithley model 610). 



