There are two containers of water having two different nails, one is nitrogen environment and another one in oxygen environment, which will corrode first? if we connect both container with wire then which will corrode first?

Hello Ashish, thank you for your question. Assuming that the nails are of exact same material, design, and surface finish, the one in the container with water+oxygen will corrode first. The reason is that the reduction reaction of water+oxygen=hydroxide will promote the anodic dissolution of the nail. This is assuming the pH is 7.   The nitrogen environment will essentially be a desecrated environment. So the hydroxide formation is not present there   HOWEVER, you have to take into account the chloride content of water if it is not deionized. You also have to consider the pH of the water. If the pH is not neutral, then there mau be different reactions.   Hence,please give more details for below parameters 1.Water content 2. pH 3. Material of nail 4. Temperature 5. Container material 6. Presence of stirring if any 7. Time of exposure.      

To answer your last question, are you connecting the containers or the nails? Can you give a small schematic for reference?