Why bending iron nails causes it to corrode faster?

[GuMing]

Homework Statement

When bending iron nails, the corrosion rate increases. Does anyone knows, why is that?

Homework Equations

The Attempt at a Solution

 

[Pkruse]

I've bent over many nails in a salt water environment, some of them I've been able to observe for as long as 40 years. I've never noticed an increased corrosion rate, except when I damaged the zinc coating.

 

[jacksonpeeble]

Oxidation occurs most easily at points of stress in a metal. This point becomes an anode for the reaction of Iron with Oxygen, yielding the half-reaction of Fe→Fe²⁺+2e^-. The reduction half-reaction, therefore, is O₂+2H₂O+4e^-→4OH^-.

There are some nice illustrations of this on pages 816-817 of Chemistry, 9th Edition by Whitten, Davis, Peck, & Stanley.

The reason for this increased oxidation at the points of stress is that the atomic structure allows the process to occur more readily. The section on Cold Worked Corrosion at http://www.efunda.com/materials/corrosion/corrosion_types.cfm has some minimal information on this, and you can always look it up in more depth if you're interested/this is the information that you need.

 

[GuMing]

Thanks for your help, guys :D

 

[DeeNos]

There are a few possible explanations for why bending iron nails can lead to increased corrosion rates. One possibility is that when the nail is bent, it creates small cracks or imperfections in the surface of the metal. These cracks can then act as sites for corrosion to occur, as they provide easier access for water and oxygen to reach the metal and initiate the corrosion process. Additionally, the bending process may also alter the crystal structure of the metal, making it more susceptible to corrosion. Another factor could be that when the nail is bent, it increases the surface area of the metal, providing more sites for corrosion to occur. It's also important to consider the environment in which the bent nail is placed - if it is exposed to moisture or other corrosive agents, this can also contribute to the increased corrosion rates. Further research and experimentation would be needed to determine the exact mechanisms behind this phenomenon.