Reason for Stress Corrosion Cracking
Reason for Stress Corrosion Cracking
(OP)
Why does the application of stress to a part produce a different corrosion mechanism other than just the type of corrosion that would occur without the application of that stress? Does thermodynamics or kinetics play a role in the process? Is it a matter of changing the fracture toughness properties (KI becomes KISCC)?
Can you please provide any sources for information that I could investigate?
Thanks.
Paul
Can you please provide any sources for information that I could investigate?
Thanks.
Paul





RE: Reason for Stress Corrosion Cracking
The theory of SCC damage mechanisms in materials is rather complex because of the wide range of variables and types of SCC damage mechanisms – intergranular and intragranular. I would suggest performing an internet search on SCC of metals, because there are many technical papers in the public domain that discuss this very subject.
RE: Reason for Stress Corrosion Cracking
RE: Reason for Stress Corrosion Cracking
I am by no means an expert in SCC damage mechanism theory. However, having been around the block a few times, my view of this is as follows; the role of thermodynamics and kinetics affects material susceptibility to SCC given certain heat treatment conditions and alloy compositions. The tensile stress is what aids in the initiation and propagation of SCC.
RE: Reason for Stress Corrosion Cracking
I always thought stress accelerated corrosion rate. But I have no idea where I got that from.
RE: Reason for Stress Corrosion Cracking
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Happy surfing.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Reason for Stress Corrosion Cracking
RE: Reason for Stress Corrosion Cracking
RE: Reason for Stress Corrosion Cracking
RE: Reason for Stress Corrosion Cracking
Since stress is usually concentrated at a crack tip, the corrosion is also concentrated at the crack tip and may not be obvious.
RE: Reason for Stress Corrosion Cracking
I think you will eventually find some basic corrosion references that will tell you that strained/stressed areas of structures are “anodic to” or have “more electronegative potential” for corrosion activity relative to lesser stressed/strained/worked areas of structures. This probably at least makes sense to most, at least to those with a basic understanding of galvanic corrosion (where all factors exist to result in same corrosion preferentially occurs at the anode, where electrons are stripped off/dissolution occurs by chemical reactions etc., not the cathode of a galvanic cell), and this can even be visibly demonstrated with various colored chemical reaction indicators. However, some who are very inquisitive (or perhaps some dense like me?) might ask further, “Why is the stressed area anodic, or why are the electrons easier to strip off/reactions with the material more likely to occur at the stressed/strained location?” I think it is at this deeper depth of questioning where you may find murkier and perhaps even some contradictory explanations.
All this being said, many years ago I heard an old professor (who I think got his Ph. D. in physical metallurgy at Rensselaer about a half century ago) once tell our class in referring to a tensile testing machine pulling a sample, “Spacing between atoms increases with elongation.” As I did not remember reading this anywhere in the text or study materials, I wrote (t)his comment down in my notes. Is it possible, in probably my too much sort of Simpleton's (and certainly not expert) thinking, that atoms or metal structures/grains etc. are sort of more accessible to reactants(ions), or being penetrated/wedged even further apart with stuff like hydrogen atoms etc. when they are “spaced” further apart or their motion is somehow affected by particularly tensile stress? To take this simplistic explanation further, at some point perhaps an increasing spacings could break bonds enough to become a “crack” (see interesting discussion of cracking at a quite micro level at http://www