corrosion data for the nickels and nickel alloys exposed on the STU 

 structures for the International Nickel Company, Incorporated. Per- 

 mission for their incorporation in this report has been granted by 

 the International Nickel Company, Incorporated, Reference 7. Results 

 from other participants in the NCEL study are also included, U. S. 

 Navy Marine Engineering Laboratory (Reference 8) and Chemistry 

 Division, NCEL (Reference 9). Deep ocean data from the Atlantic Ocean 

 (References 10 and 11), surface data from the Atlantic Ocean (Reference 

 12) and surface data from the Pacific Ocean (References 13 and 14) 

 are included for comparison purposes. 



NICKEL 



The chemical compositions of the nickels are given in Table 2, 

 their corrosion rates and types of corrosion in Table 3, and changes 

 in mechanical properties in Table 4. 



Nickel is passive (resistant) in moving sea water but is subject 

 to local attack or pitting in stagnant sea water. Fouling organisms, 

 deposits, and crevices cause pitting and crevice (oxygen concentration 

 cell) corrosion. 



The corrosion rates and types of corrosion of seven nickels (94 

 percent minimum nickel) are given in Table 3. Crevice corrosion and 

 edge corrosion (on the ends) were the two types which were respon- 

 sible for practically all the corrosion damage. Corrosion rates 

 calculated from weight losses are most meaningful and valuable when 

 the type of corrosion is either uniform or general; therefore, cor- 

 rosion rates for nickels would not be the best criteria for assessing 

 corrosion. To obtain a complete evaluation of the corrosion of an 

 alloy, corrosion rates, maximum and average pit depths, pitting fre- 

 quency or pitting factor, type of corrosion, changes in mechanical 

 properties, and resistance to stress corrosion cracking should be 

 determined. 



In the case of the nickels, there was very little surface cor- 

 rosion so little emphasis can be placed on corrosion rates. The two 

 types of corrosion encountered (crevice and edge penetration) can 

 be extremely damaging from the standpoint of reliability. The edge 

 penetration was caused by the microcracks formed during the shearing 

 operation which illustrates dramatically the corrosion damage which 

 can be caused by this fabricating procedure. Penetration of as much 

 as an inch during six months of exposure was found. For sea water 

 applications, shearing or punching of holes should not be permitted; 

 only sawing, machining or drilling. 



