CORROSION OF MATERIALS IN HYDROSPACE - PART I. IRONS, STEELS, 

 CAST IRONS, AND STEEL PRODUCTS 



Technical Note N-90G 



Y-F015-01-05-002A 



by 



Fred M. Reinhart 



ABSTRACT 



A total of 1300 specimens of 47 iron base alloys were exposed 

 at depths of 2,340, 2,370, 5,300, 5,640 and 6,780 feet at two sites 

 in the Pacific Ocean for 197, 402, 1064, 123, 751 and 403 days 

 respectively to determine the effects of deep ocean environments 

 on their corrosion behavior. 



Corrosion rates, pit depths, types of corrosion, changes in 

 mechanical properties, effects of stress, and analyses of corrosion 

 products are presented. 



The corrosion rates of all the alloys, both cast and wrought, 

 decreased asymptotically with duration of exposure and became con- 

 stant at rates varying between 0.5 and 1.0 mils per year after three 

 years of exposure in sea water and partially embedded in the bottom 

 sediments at a nominal depth of 5,500 feet. These corrosion rates 

 are about one-third those at the surface in the Atlantic Ocean. 



At the 2,350 foot depth, the corrosion rates in sea water also 

 decreased with duration of exposure but tended to increase slightly 

 with duration of exposure in the bottom sediments. 



The corrosion rates at the 2,350 foot depth were less than 

 those at the 5,500 foot depth. 



The mechanical properties were unimpaired. 



Silicon and silicon-molybdenum cast irons were uncorroded. 



A sprayed 6 mil thick coating of aluminum protected steel for 

 a minimum of three years and a hot dipped 4 mil thick coating of 

 aluminum protected steel for a minimum of 13 months while a hot 

 dipped 1.7 mil thick coating of zinc protected steel for about 4 

 months. 



