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Why does certain parts of metal show more corrosion at the place where there is high dislocation density in comparison to the place where the dislocation density is less? I do sincerely feel that this is particularly because of the fact that the activity is less in that particular localized region where the corrosion is taking place. I think the situation is similar where grain boundaries act as stressed region but what has this to do with the activity. A detailed answer to the above situation will most certainly be welcome.

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In the real world ,I don't believe I have seen CORROSION at STRESSED areas. Corrosion may be accelerated at STRAINED areas; the strains introduce energy to the microstructure which may promote corrosion. Cracking is another story - which you did not ask about . Hydrogen cracking of high strength steels is likely the most common case . It can often occur with no apparent corrosion ; In particular cathodic protection which prevents corrosion ,can introduce hydrogen which causes cracking.

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  • $\begingroup$ I am not sure I understand the actual difference your are exclamating between stressed and strained. In the hope of understanding this, would you mind providing a common case example, were a material is stressed but not strained, or the opposite? $\endgroup$
    – NMech
    Feb 7 at 6:03
  • $\begingroup$ My bad , I meant plastic strain. Any component will normally be under stress and elastic strain. $\endgroup$ Feb 8 at 0:37
  • $\begingroup$ Ok, that makes more sense. Essentially, if I get it correctly, you associate the dislocations that occur during the plastic strain with the onset of corrosion. $\endgroup$
    – NMech
    Feb 8 at 8:17
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One of the mechanism that affect corrosion is known in the literature as Stress Corrosion Cracking (SCC). The idea is that tensile stressed regions are prone to crack development. Crack development essentially maximizes the area that corrosion can develop. Since corrosion, degrades the properties of the material, this accelerates further the crack development so its a downward spiral.

However, like you might have suspected:

  • tension tends to have adverse effects while
  • compression tends to mitigate stress corrosion cracking.

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There is a lot of literature in the subject. A quick google search yielded the following articles:

  • Effects of compressive stress on localized corrosion in AA2024-T3 Xiaodong Liu, G.S. Frankel, DOI: 10.1016/j.corsci.2005.12.003
  • John Beavers, Thomas A. Bubenik, in Trends in Oil and Gas Corrosion Research and Technologies, 2017
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