David L. Johnson' may have said:On Wed, 16 Jul 2003 15:52:28 +0000, W K wrote:
Quoted message said:sacrificial anodes only work to protect a more reactive metal. As it goes iron<zinc<Al<Mg
Quoted message said:Zinc will protect iron (hence steel), but could not protect Al
True; I didn't check first. Zinc's presence would have no effect or might accelerate corrosion of
aluminum. But, as you noted, aluminum doesn't have as severe a problem with corrosion as steel in
most cases, although it's actually worse under some conditions.
Quoted message said:Quoted message said:All of this though is complicated by the way alloys can have slightly surprising properties, and
the way that something with a low % of magnesium and massive % of Aluminum could be called a
"magnesium alloy" ... which would then be shortened to "magnesium"Just like those "scandium" bikes.
Or vanadium tools, for that matter.
Sometimes, though, a buzzword can be flung up in the air by way of intentional misdirection.
In the '70s, Porsche had made a few race-only 911s with aluminum bodies as an engineering exercise;
they were doing quite well on the circuit, and one of the drivers had become very tired of the
magazine reporters' badgering about "What's the new body made from, really?" (Porsche was being very
tight-lipped about it at the time.) So, he decided to have a little fun with them. At a gathering
before a major race, he told them the body was made from unobtanium. A few of the reporters (the
ones most fluent in English) gave up pestering him at that point, but several asked him how that was
spelled....and at least two magazines actually published the report.
And yes, a lot of Mg/Al alloys get called "Mag", the same way that
Cr/Mo steel (which is still mostly iron in the majority of useful alloys) is designated by its
perceived most important but actual minority components. The same observation goes for titanium
drill bits, most of which have a submicroscopic film of titanium on their surface, and none at
all in the alloy.
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