electromechanical cable just above the tracking arm assembly was heavily 

 coated with copper-based antifouling compound. The red deposits were 

 assumed to be copper (which was later verified) which would explain the 

 localization of the attack of the aluminum structure most directly 

 beneath the source of copper. The aluminum structure in electrical 

 contact with the 70-30 cupro-nickel hydrophone cases at the ends of the 

 tracking arms was severely corroded by galvanic action. 



Array Counterweight Cable 



Approximately 10 feet of the 3.75-inch wire rope array counterweight 

 cable was available for inspection. The outer wires were 100% rusted. 

 However, corrosion of these wires was not severe. No broken wires were 

 located. The inner strands of the cable had retained much of their 

 original lubricant coating. The inner strands of the cable were essentially 

 uncorroded. 



LABORATORY EVALUATION 



Samples of joints from both the steel and aluminum portions of the 

 tracking arm assembly were returned to CEL for analysis. Also, several 

 samples of corrosion products from various portions of the array and 

 several small hardware items were retained by CEL for analysis. - 



Evaluation of Tracking Arm Joints 



The aluminum tracking arm joint was analyzed chemically and found 

 to be aluminum alloy 6061 . Chemical analysis of the weld metal was 

 typical of deposits obtained with 5356 welding wire. The maximum pit 

 depth measured on this section was 0. 200 inch. The pits were randomly 

 distributed with a frequency of ssl pit per square inch. Microstructural - 

 analysis showed these pits to be intergranular in nature. The weld 

 beads were less corroded than the adjacent parent metal. There was no . 

 accelerated attack at the heat-affected zones adjacent to the welds. It , 

 was noted, however, that corrosion was accelerated at areas which had 

 been covered with electrical tape during exposure. Mechanical tests of 

 the section resulted in failures of the tubular sections; the weld 

 joints did not fail. The ultimate strength of the tube sections averaged' 

 56% of the rated breaking strength of unexposed 6061 -T6 tube. However, 

 the elongation was reduced from a rated 12% to an average of 4%. This 

 reduction of elongation is typical of aluminum alloys which are subject 

 to pitting. 



The steel section of the structure was analyzed chemically and 

 found to be typical of A- 36 structural steel. The section was corroded 

 uniformly. Tensile tests of coupons from the tubes showed no loss of 

 material properties compared with typical properties of A-36 steel. 



