Reinhart 



Type 316 wire rope lost 40 percent of its strength after 1,064 days of 

 exposure at a depth of 5,300 feet because of crevice corrosion of the 

 internal wires. The breaking strength of the galvanized plow steel 

 (0.83 oz Zn) was decreased by 17 percent. The breaking strengths of 

 the other six wire ropes were unaffected. Although there was no loss 

 in the breaking strength of the 18 percent chromium- 14 percent man- 

 ganese stainless steel rope there were quite a number of broken 

 wires due to corrosion both on the outside and on the inside strands. 



Metallic Coatings 



Zinc, aluminum, sprayed aluminum and titanium-cadmium 

 coated steel specimens were exposed at depth. 



The galvanized steel (1.0 oz per sq ft) was covered with a 

 layer of flaky red rust after 402 days of exposure at a depth of 

 2,370 feet. The corrosion rates were 0.9 MPY for the specimens ex- 

 posed in the sea water and 0.4 MPY for the specimens partially em- 

 bedded in the bottom sediment. The corrosion rate for bare steel 

 (AISI 1010) in sea water under the same conditions was 1.2 MPY indi- 

 cating that the zinc coating was removed within a short period of 

 time 93 to 4 months). The difference in corrosion rates in the 

 bottom sediment was 0.7 MPY which shows that the zinc coating pro- 

 tected the steel in the bottom sediment for at least twice as long 

 as it did in the sea water. There was no loss in the mechanical 

 properties of the galvanized steel. 



The aluminized steel (1.03 oz per sq ft) was covered with 

 white corrosion products, spotted with a few specks of red rust after 

 402 days of exposure at a depth of 2,370 feet. About 22 percent of 

 the aluminum coating was corroded from the specimens exposed in the 

 sea water and 40 percent was corroded from the specimens partially 

 embedded in the bottom sediment; the underlying steel had not cor- 

 roded. Therefore, it can be concluded, on a weight basis, that 1 oz 

 per sq. ft. of aluminum will protect steel for a longer period of 

 time than 1 oz per sq. ft. of zinc; about 4 times as long in sea 

 water and about 2 times as long when partially embedded in the 

 bottom sediment. 



A titanium- cadmium coating on AISI 4130 steel was completely 

 sacrificed and the steel was covered with a layer of red rust after 

 402 days of exposure at a depth of 2,370 feet. 



A 6 mil thick, sprayed aluminum coating which had been 

 primed and sprayed with 2 coats of clear vinyl sealer protected the 

 underlying steel for 1,064 days of exposure at a depth of 5,300 feet. 

 After removal from exposure the aluminum coating was dark gray in 

 color, speckled with pin point size areas of white corrosion products. 



Cast Irons 



The corrosion rates for the gray, nickel, nickel-chromium, 

 silicon, silicon-molybdenum and ductile cast irons at the two nominal 

 depths in the Pacific Ocean are shown graphically in Figure 10 for 

 sea water. 



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