Pitting corrosion of nanocrystalline metals

11 Potentiodynamic polarization plots of 309 stainless steel in 3.5% NaCI solution. 

12 Current electrochemical noise of the coarse crystalline austenitic stainless steel (a) and the corresponding NC coating (b) under anodic polarization during 600-800 s in 3.5% NaCI solution.  

13 In situ AFM images of the coarse crystalline alloy in the pitting stage under anodic polarization in 3.5% NaCI solution (a) the formation of a metastable pit, (b) the growth of the pit, (c) the reparation of the pit and (d) the growth of the pit.  

Generation and reparation of metastable pits were not observed on an austenitic stainless steel NC coating, nor was the process of metastable pitting. Once the pit formed, it grew directly to a stable pit state (in Fig. 4.14) with subsecpient dissolution of the sample. This observation suggests that the pits formed at the 

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