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Offline river6109  
#1 Posted : 18 May 2023 06:02:11(UTC)
river6109

Australia   
Joined: 22/01/2009(UTC)
Posts: 14,636
Location: On 1965 Märklin Boulevard just around from Roco Square
Murat Tiryakioglu wrote on facebook:

First Results on the Disintegration of Marklin Trains Produced during WW2:
I spent two days with colleagues in front of a scanning electron microscope looking at the pieces of an SK800 tender that disintegrated. Although literature states that it is the lead (Pb) content of the alloy that causes this disintegration, we found absolutely no links between the Pb content and swelling and disintegration.
It was very clear on fracture surfaces that Marklin was struggling to get good zinc (Zn) and aluminum (Al) ingots, and was using scraps (both Zn and Al) to get the melts for their die castings. The pieces we looked at were full of pores, bubbles and oxide films. These casting defects formed a network, which allowed air to get inside the castings. This started a VERY slow process of transforming Zn to zinc-oxide (ZnO). ZnO is the white powder that we see on some tenders from 50s. When it is on the surface, it is only a nuisance. But when Zn transforms into ZnO INSIDE the casting (tender), it causes an expansion because ZnO is less dense than Zn. This is the reason for the swelling. It will go on until the train completely disintegrates.
So here is what I learned: I really need to cover my swollen tenders and cut their contact with atmosphere. Otherwise I will not have them as one piece for long.
I will post some pictures in late summer.
https://www.youtube.com/river6109
https://www.youtube.com/6109river
5 years in Destruction mode
50 years in Repairing mode
thanks 9 users liked this useful post by river6109
Offline Toosmall  
#2 Posted : 18 May 2023 09:23:07(UTC)
Toosmall

Australia   
Joined: 26/07/2021(UTC)
Posts: 608
Location: Sydney
On a lead health issue note.

The fisherman (people) around my area are handling lead weights. Being doing it for decades.

If one has kids, fair enough, be sensible. But I'm still going to use lead/tin solder... with good ventilation!
Offline Henrik Schütz  
#3 Posted : 18 May 2023 09:32:57(UTC)
Henrik Schütz

Sweden   
Joined: 04/08/2015(UTC)
Posts: 74
Location: Stockholms Lan, Stockholm
Originally Posted by: river6109 Go to Quoted Post
Murat Tiryakioglu wrote on facebook:

First Results on the Disintegration of Marklin Trains Produced during WW2:
I spent two days with colleagues in front of a scanning electron microscope looking at the pieces of an SK800 tender that disintegrated. Although literature states that it is the lead (Pb) content of the alloy that causes this disintegration, we found absolutely no links between the Pb content and swelling and disintegration.
It was very clear on fracture surfaces that Marklin was struggling to get good zinc (Zn) and aluminum (Al) ingots, and was using scraps (both Zn and Al) to get the melts for their die castings. The pieces we looked at were full of pores, bubbles and oxide films. These casting defects formed a network, which allowed air to get inside the castings. This started a VERY slow process of transforming Zn to zinc-oxide (ZnO). ZnO is the white powder that we see on some tenders from 50s. When it is on the surface, it is only a nuisance. But when Zn transforms into ZnO INSIDE the casting (tender), it causes an expansion because ZnO is less dense than Zn. This is the reason for the swelling. It will go on until the train completely disintegrates.
So here is what I learned: I really need to cover my swollen tenders and cut their contact with atmosphere. Otherwise I will not have them as one piece for long.
I will post some pictures in late summer.


Tenders from the 50s are cast from magnesium, not zinc. Only the very last sk800 tenders are zinc (zamac) they are much heavier than the magnesium ones. Magnesiomoxide is white powder, and it forms on many magnesium tenders.

Henrik

thanks 4 users liked this useful post by Henrik Schütz
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