SECTION 9 

 WIRE ROPES 



Wire ropes of many different chemical composi- 

 tions, with different types of coatings, of different 

 sizes, and of different types of construction were 

 exposed in seawater at depth to determine their 

 corrosion behavior. Some were stressed in tension to 

 determine their susceptibility to stress corrosion or 

 whether stress increased their rates of corrosion. 



The chemical compositions of the ropes are given 

 in Table 88, and their corrosion behavior in Table 89. 



There was no visible corrosion on rope numbers 

 15, 18, 19, 20, 21, 22, 41 (751 days, 6,000 feet), 48, 

 49, 50, 51, 52, and 53. Rope number 15 was Type 

 316 stainless steel modified by adding silicon and 

 nitrogen and was exposed for 189 days at the 

 6,000-foot depth. Wire rope number 41, conventional 

 Type 316, was uncorroded after 751 days of expo- 

 sure at the 6,000-foot depth, but was rusted with 

 some internal wires broken and crevice corrosion 

 after 1,064 days of exposure; its breaking strength 

 was decreased by 41% after 1,064 days of exposure at 

 the 6,000-foot depth. Because the conventional Type 

 316 stainless steel was not corroded until between 

 751 and 1,064 days of exposure, it cannot be stated 

 that the addition of silicon and nitrogen to the Type 

 316 stainless steel improved its corrosion resistance. 



Rope numbers 18, 19, 20, and 21 were nickel 

 base alloys. Rope numbers 20 and 21 were also 

 uncorroded when lying on or in the bottom sediment. 



Rope number 22 was a cobalt base alloy which 

 was also uncorroded when lying on or in the bottom 

 sediment. It, also, was not susceptible to stress cor- 

 rosion in either the seawater or the bottom sediment 

 when stressed to 40% of its breaking strength. 



Rope numbers 48, 49, 50, 51, 52, and 53 were 

 6A1-4V-Ti ropes and wires. The ropes and wires them- 

 selves were not corroded, but the Type 304 stainless 

 steel fittings and steel tie wires were severely 

 corroded galvanically. 



All the other wire ropes, coated or uncoated, 

 were corroded to varying degrees of severity, the 

 most severe being the parting of the wires. 



Bare steel wires 1, 2, 3, 35, and 36, as expected, 

 were completely covered with rust. There was no loss 

 of strength after periods of exposure of as long as 



1,064 days. These ropes had been lubricated during 

 fabrication; the lubricant on the outer surfaces of the 

 ropes had disappeared, but not on the internal 

 surfaces during exposure. One rope, No. 2, was 

 degreased prior to exposure; as a result, it was more 

 severely corroded than the others on the outside sur- 

 faces, and there was light rust on many of the internal 

 "^SRx9. One rope, No. 3, was degreased, then wrapped 

 with 10-mil-thick polyethylene tape prior to expo- 

 sure. There was heavy rust underneath the tape for a 

 distance of about 3 feet from each end and there was 

 light rust on about 75% of the internal wires. Wires 

 35 and 36 had been stressed in tension to 20% of 

 their respective breaking strengths prior to exposure. 

 These two ropes were covered with rust with no rust 

 on the internal wires, did not fail by stress corrosion, 

 and had no decrease in'their breaking strengths. 



The galvanized (zinc-coated) ropes were numbers 

 4, 5, 6, 23, 24, 25, 26, 27, 28, 37, and 38. The zinc 

 coatings protected the steel wires, but there was no 

 good correlation between the weight or thickness of 

 coating and the duration of protection. In general, 

 except for the electrogalvanized coating, the heavier 

 the coating the longer the period of time before rust 

 appeared on the ropes. The breaking strengths of the 

 ropes were not impaired by exposures for as long as 

 1,064 days of exposure. Also, rope numbers 37 and 

 38 were not susceptible to stress corrosion when 

 stressed to 20% of their respective breaking strengths. 



Rope numbers 7, 8, 9, and 40, in addition to 

 being galvanized, were also jacketed with plastic 

 coatings. In all cases, seawater penetrated along the 

 interfaces between the ropes and the jackets. There 

 was some light rust on the strands of rope number 40 

 underneath the poly (vinyl chloride) jacket after 751 

 days of exposure. The polyurethane (rope number 7) 

 and polyethylene (rope numbers 8 and 9) jackets 

 protected the galvanized ropes to a considerable 

 extent. The jackets were not punctured or broken, 

 but seawater had penetrated to the metal ropes 

 through the end terminations. That water had pene- 

 trated to the interface between the jackets and the 

 ropes was proven by puncturing the jackets, at which 

 time seawater spurted out under considerable 



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