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Bertram31.com General Bulletin Board
Re: Coast Guard Response to Ethanol Questions
Posted By: Peter In Response To: Coast Guard Response to Ethanol Questions (Chiles)
Date: Tuesday, 4 April 2006, at 5:57 p.m.
Thanks, Chiles;
For anyone interested, crevice corrosion is a point of corrosion that begins in a tiny (microscopic) crevice or pin-hole in the surface of the stainless. The oxygen can't get into the crevice to create the protective chromium-oxide layer that prevents stainless from rusting--usually because something else like salt water or gasoline is already in the crevice and therefore in the way-- so a corrosion process can begin.
Once the corrosion begins it can create a crack. Such a crack can progress through the steel at an amazingly fast rate resulting in a sudden failure. Think of stressing the area with only 100 lbs of load, but the brunt of that load gets focused on the teeny tip of the crack which might be as small as a 0.0001 inch. Local stresses can getto 10,000,000 lbs per squre inch in such a case, and boom! the crack takes off, tearing accross the weld or what have you.
The good news is that modern welding techinques make it a whole lot easier to avoid such crevices than it used to be. Also post-welding treatment to "Passivate" the surface, which is basically just getting the chromium oxide layer going, can help. Personally if a reputable weldor in a good shop with the right equipment (i.e. TIG welder) performed the work I'd have no worries about it.
As for copper stainless steels and copper nickel steels like Hastelloy and Inconel, well these are more corrosion resistant, but I question the effects of ethanol on copper since it has bad reactions to other "soft" metals including brass which contains copper.
Galvy coated is out because etanol doesn't like zink.
Steel or iron are approved, but then what do you coat it with? And is the coating going to be compatible?Like every other turn in this mess each question leads to more questions and very few answers.
I still want to know if ethanol fumes are lighter than air and if they are going to collect near the top of my engine box by the blower motor, instead of the bottom of the engine box near the blower pick up. Anybody? Who wants to be the first to flip the switch?
Thanks again Chiles for posting the information.
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