sleeves the fact that these portions of the housings were more severely 

 attacked than the housing bodies can be explained by this effect. 



Hydrophone Cases 



The hydrophone cases were fabricated from either 90-10 cupro-nickel 

 or 70-30 cupro-nickel. The 90-10 cupro-nickel housings were uniformly 

 etched and had a thin blue-green patina on much of their surfaces. The 

 weld beads and heat-affected zones were in the same condition as the 

 remainder of the housings. No difference in attack was noted in the 

 housings exposed at different depths. 



The hydrophone cases fabricated from 70-30 cupro-nickel were also 

 uniformly corroded except for some shallow linear attack in the heavily 

 deformed hydrophone support tubes. No accelerated weldment attack was 

 noted. 



All the monel bands used to secure the protective rubber boots to 

 the hydrophone supports showed some signs of crevice corrosion, particularly 

 at the band joining buckles. Two bands were found to have completely 

 failed. 



The insulating blocks used to electrically isolate the hydrophone 

 cases and other copper-alloy instrument cases from their respective 

 steel termination housings had retained their original effectiveness. 

 Resistance between the cases and the housings was in excess of 1,000 

 ohms. 



Tracking Arm Assembly 



The tracking arm assembly consisted of a steel center section with 

 aluminum outer sections. The steel center section was covered with a 

 very thin layer of tan corrosion products as is typical of the corrosion 

 products on galvanized steel after depletion of the zinc coating. No 

 copper deposits were noted on the steel structure. No significant 

 corrosion of the steel structure was evident. At the ends of the open 

 tubular sections of the central portion of the tracking arm assembly 

 there were stalactite like rust tuber cules. These tubercules were up to 

 8 inches long and 2 inches in diameter. Their hard outer skins (1/4- 

 inch thick) covered softer and often fluid interiors. After several 

 hours exposure to the air the tubercules became brittle and crumbled. 

 The interior portions of the tubular steel members which showed these 

 tubercules were uniformly corroded. 



The aluminum sections of the tracking arm assembly were heavily 

 corroded. This corrosion was most severe on the portions of these 

 sections nearest the steel center section. As the aluminum and steel 

 were separated by nonmetallic isolation blocks which had retained an 

 insulation resistance of over 1,000 ohms between the steel and aluminum 

 sections, galvanic corrosion between the dissimilar metal sections was 

 not the cause of this localization of attack. There were, however, red 

 deposits on the central portions of the aluminum tracking arms. The 



