That's what I was thinking Ralph, that some of those in that updated style that I had seen had to be zinc. The one to its left has a very nice finish.
That's what I was thinking Ralph, that some of those in that updated style that I had seen had to be zinc. The one to its left has a very nice finish.
No indication is found where specifically it is said they were made from zinc.
I can't get zinc confirmed!
All over the years (1936-1939) they were mentioned to be manufactured from
Leichtmetall, which looks as aluminum (with the naked eye one cannot
see the difference). Since about 1939 they were mentioned to be from aluminum.
Also this Leichtmetall and aluminum can have what is called "pest" (see
enclosed eagle).
its a v/nice piece.
That is fascinating stuff Wilhelm. It would be interesting to have metallurgy tests done on one to see what is in that alloy mixture. I wonder if the pesting on leichtmetall is as catastrophic as it is on zinc pieces? It certainly looks very similar to a zinc badge to the eye, which is no doubt why all the confusion on them.
The components for Leichtmetall (Al-Mg-Si-1) should be as according
to the information from Overhoff-concern, I got:
Cu 0.036
Zn 0.033
Mg 0.828
Mn 0.702
Si 1.004
Fe 0.326
Ti 0.038
And no the pest is not so catastrophic as with zinc pieces. Not at all!
Possibly the components for the shown eagle are not to as according
to procedures. It even looks as a gilded one, but with an extremely
heavy patina!
So, the composition is:
Copper
Zinc
Magnesium
Manganese
Silicon
Iron
Titanium
Now, we're really getting beyond my depth here, but it looks like it shares similarities with the zamac we see in many mid to later period badges using a base metal of zinc and alloying elements of aluminium, magnesium, and copper. Even though Leichtmetall doesn't appear to rely so heavily on zinc, perhaps it shares some of the issues from impurities in the mix causing pesting as zamac pieces of the period did?
I won't begin to purport I fully understand this, but based on a research paper I found on this alloy composition (see below for a snippet) it appears the type of aluminum alloy we're talking about as Leichtmetall is usually very corrosion resistant (often used in automobile and airplane bodies), but can exhibit corrosion due to iron-containing intermetallics combined with overuse of silicon in an attempt to obtain higher mechanical strength. Technology back then certainly couldn't assess all of the microscopic changes in the metal we can test for today, but variations in these elements of the mix might well explain why some of these have held up so well over decades, while others have taken an appearance more like the typical zamac piece. Interesting stuff!
From a research paper:
Zahavi et al. (1982) and Ambat et al. (2006) reported that Al alloys frequently exhibit a number of troubles related to localized corrosion attack, despite the significant corrosion resistance typically obtained in these alloys which are passive in the pH domain ranging from 3 to 8 [12-13]. Besides, on behalf of the low solubility limit of alloying elements intermetallics form, which induces heterogeneities that play a significant role in the local distribution and rate of cathodic and anodic reactions. For Al-Mg-Si alloys, intermetallics and grain boundaries are seen as the main anodic corrosion initiation sites, and most of intermetallics increase the corrosion rate due to their cathodic nature [13-16]. The main intermetallics present in Al-Mg-Si alloys are Fe-containing intermetallics (noble compared to the matrix) and MgSi precipitates which possess an ambivalent electrochemical behavior.
Generally, it has been reported that the excess of Si (which induces a major precipitation of MgSi), added in Al-Mg-Si alloys mainly to obtain higher mechanical strength, leads to a greater intergranular corrosion susceptibility. The MgSi particles have shown, for various aluminum alloys, active anodic dissolution of Mg within seconds after immersion in aggressive chloride-containing solutions [17-20].
The material structure was for me not important, as my investignation was
in those days only related to the manufacturing of buckles and to know about
the difference between aluminum and light-weight metals (Leichtmetall). I never
did further research here.
What I know is that Leichtmetall, which is quite soft (ursprünglich weich), was
hardened (ausgehärtet) or vergütet (which is the same) to get strength.
Overhoff mentioned the hardened Leichtmetall as "aushärtbares Leichtmetall",
which then was prescribed as AlMgSi.
Overhoff never mentioned zamac, which most important component is zinc (I read at
Wikipedia)! If Overhoff would have used this material for the manufacturing (for
example of buckles) they surely would have mentioned it.
My technical knowledge does not go deeper. Sorry, I can't be of more help here!
You were plenty of help Wilhelm!
I know far more about these lanyards and materials than when I posted it. Many thanks.
Similar Threads
Posting Permissions
.
Bookmarks