User talk:Equinox2
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[edit] SCC
I query your suggestion that pure metals are not susceptible to SCC. Acids and alkalis will attack many pure metals and pure copper is attacked by ammonia. Peterlewis (talk) 16:14, 3 June 2008 (UTC)
Hello Dr. Lewis. It's nice to meet you. Let's discuss this and end up with a page we are both happy with. It's clear that both of us are knowledgable in this field.
First off, note that my statement says that "generally", thus a few exceptions may occur, but this is not the norm. Next, could you clarify about your statement "Acids and alkalis will attack...". I fully agree that they will "attack" many pure metals, but are you saying that they cause pure metals to undergo SCC?
About the Cu, which alloy designation do you mean (such as alloy C11000, which is ETP pure copper)? The susceptability of various copper materials are listed on pg. 7-38 of the ASM handbook, and it lists the higher purity alloys as having an SCC susceptability of 0 (compare to, say, alloy C35300, which has a susceptability of 1000). Sometimes I've seen alloys of Cu referred to as "copper". Perhaps this is what is happening here?
I want to rely more on referencable sources than on personal experience, but I haven't seen any pure metals SCC, and have seen quite a bit of SCC over the years. Equinox2 (talk) 16:31, 3 June 2008 (UTC)
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- The reason SCC is or has not been commonly seen in pure metals is surely that pure metals are rarely used as structural materials. Most SCC papers come from practical problems such as season cracking with brass cartridges. There is no inherent reason why pure metals should be less susceptible to SCC than alloys. Peterlewis (talk) 22:51, 3 June 2008 (UTC)
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- Thanks for the reply. While I agree that alloys are used more often than pure metals, there are plenty of applications for pure metals, such as electrical components of pure Cu, Ag, etc, as well as piping (such as pure Ni (Ni200), Ta, etc. Are there specific situations you are thinking of for the SCC of pure metals? Maybe I'm unaware of the specific examples you are thinking of. Also, were you going to get the alloy designation for the copper SCC you referred to in your first post? Thanks- Equinox2 (talk) 12:39, 4 June 2008 (UTC)
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One of the problems with SCC is that relatively little seems to be published. But absence of evidence is not evidence of absence. SCC involves chemical reaction of a metal with any number of different chemicals at low concentrations, and I see no reason why pure metals should be exempt from attack. Peterlewis (talk) 15:09, 4 June 2008 (UTC)
- It's certainly true that the full mechanism of SCC (any SCC, either in alloys or pure metals) isn't known for certain based on published materails. However, empirically noted trends (such as the dependance on specific chemicals like Cl- in SS) are valid things to be listed in the wiki. At the same time, mechanisms have been discussed. At metallurgical conferences I've heard various reasons for the lack of SCC in pure metals discussed, such as the fact that SCC is linked to stress, and the creation of a stress field around solute atoms (there's much more to it than that greatly simplified description). Many have noted that pure metals generally don't undergo SCC, and many reasons have been discussed. We don't just have a lack of evidence, we do have evidence of absence. There are many cases of SCC reported, and many cases of pure metals being used in all kinds of environments, yet many of us materials scientists have noted, and written about, the fact that pure metal SCC is rare. Do we agree that that's not just an absence of evidence?
