My apologies to Dr. Graham
Yesterday, I realized that my words had drastically missed there mark and intent and that I owe sincere apologies to Phil.
While it was occuring, I found our exchange to be extremely funny. But since it is clear that only Phil and I share the common background on which the joke was based, and since he didn't get the joke, my private amusement instead comes across as mean spirited.
In no way was my intention to prove Phil wrong and myself correct. My actual belief is that in science we build models of understanding and it is necessary to recognize those models and their limitations. Fermi has always been a hero of mine, not so much for his science, but for his philosphy of science and how he shared that with his students. A major part of his use of "Fermi questions" was to force the student to define the assumptions the model is built on.
I had always sort of assumed the Phil was full time in the audio business because of his extensive knolwedge. As the chemistry posts rolled on, I found humor in his responses because they matched a bias I have against the research practices in American Academia, due to my own experiences in the same. Then towards the end, I remembered his posting about the nuclear incident. It became clear to me that Phil must be a research chemist of some experience (or since I thought he is young enogh, he may prefer the newer title of materials science). Based on the way he responded, I would have guessed a specialization in nanochemistry and surface process (interactions at phase boundarys). The humor was based on my cynical view that someone preparing to defend their dissertation is basically trained to consider every POSSIBLE condition, rather than focusing on PROBABLE. In other words, I found it funny that Phil answered exactly like a chemistry doctoral candidate or post doc would respond.
Imagine my embarrassment when a quick google search should that is exactly what he is.
What he probably didn't know was that he had caught himself a ringer. While I have never really hidden that I now teach Chemistry full time, I really haven't talked too much about my research background, except for a couple of threads that touched on experimental design and statistics.
I spent 12 years (all of the 1990's) working in research specializing as an analytical chemist working with naturally occuring waters (especially estuarine and marine) and the sediments associated with them. Much of that work included naturally occuring anoxic situations. Therefore, I was hiding the fact that I really had prior knowledge of the situation I set up and was asking questions about.
Warning- chemistry geeking, if you don't care about chemistry skip this part...
I would consider this situation to be a descrepent event. The actual explanation is not apparently obvious, and I used that knowledge to eliminate parts of Phil's responses, when they started to approach the accepted explanations, rather than simply stating what I believe the current research shows (at least current based on ten years ago, but I haven't heard of any groundbreaking changes.)
For the record, in the absence of water, the thermodynamically most favored reduction reactant is H+ from the water itself. This process is kinetically limited by the availability of the H+. This is obviously also pH dependent. To my best knowledge, the low temperature formation of magnetite in naturally occuring anoxic water (I believe it was groundwater in the study I remember) is at a rate of approximately 1 um per year for cast iron, or 100 nm per year for carbon steel. Would this be of interest to a nanochemist? Yes. Would this be of interest to an engineer looking at long term storage of spent nuclear wastes where there might be contact with ground water? I hope so? Would the average scientist not specializing in those fields look at the material and say it was corroding on a couple of months time scale for exposure?
The second most common reduction reactant in anoxic systems is sulfur. The reduction of sulfur is less thermidynamically favorable but far more kinetically favorable. The sulfur reaction is extremely pH dependant, so it varies greatly depending on local conditions.
Probably the most important mechanism was the one that was never mentioned. There are actually numerous bacteria forms, especially in sediments that biooxidize iron. This often can account for the greatest amount of corrosion.
If you want to consider the possibility of a concentration cell, the average concentration of dissolved iron in seawater is 2-3 ppm, most of that already in the oxidized hydroxide form. One process that I know exists but am not as familiar with the details of is that in many deep sea situations the iron can actually be reduced and precipitated as iron metal.
I would still maintain that BECAUSE the Gibbs thermodynamic description does not consider reaction rates, that is exactly why we need to consider it separately when describing a situation. At this level of understanding, we build our private models of knowledge, and if Phil and I ever meet in person we can shake down that idea with a very dull argument from the standpoint of everyone else.
Chemistry geeking over, apology resumes...
Anyway, once again, I am sorry, my intention was not to try to set up a situation where I was right and Phil was wrong, but Phil, you tickled my cynacism bone when you responded exactly as you were trained and as American academia depends. My humor was directed at that system, not at you personally.
P.S. Did you know Gardiner Myers at UF. I worked for 1 week a year with him scoring AP papers during the early 2000's
