The black coating is most likely Ferric oxide(Fe3O4) with some Ferrous Oxide admixture. Both of these compounds are black,whereas aluminum oxide(alumina) is chalky white. The iron oxide was form from the head tube during electrolytic corrosion while in contact with the aluminum stem. Art-trying to remember chemistry- Link,San Antonio,TX
Bianca Pratorius <biankita@comcast.net> wrote: To: classicrendezvous@bikelist.org From: Bianca Pratorius <biankita@comcast.net> Date: Wed, 2 May 2007 20:16:39 -0400 Subject: [CR]Thanks to all ... Stuck stem now freed
I finally tapped the stuck stem out using a rubber mallet on the underside. In the bargain, I now have a Campy Super Record headset with French sizing. (who knew that an Italian bike like an ALAN would have a french Campy headset.) Interestingly enough, the part of the stem which was stuck in the fork tube turned black! What's that black coating? The part of the stem which touched the bars also is coated with some kind of uniform blackness. Is this some kind of Aluminum oxide?
Garth Libre in Miami Fl. USA
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