Tin plague
Tin plague is an allotropic transformation of tin that destroys tin objects.
It is to be differentiated from tin corrosion , a chemical corrosion process caused by the inclusion of aggressive substances in the surface . Tin plague is also not related to zinc plague , a corrosion process of zinc .
Silver-white β-tin, which is resistant from 16 ° C to 181 ° C, transforms into gray-black α-tin below 13.2 ° C. Both have different crystal structures and densities (see properties of tin ).
This transformation emanates from individual centers and slowly spreads. It manifests itself on pewter objects as large and small spots, followed by wart-like vesicles on the surface that fall apart when lightly touched. Since α-tin takes up a larger volume than β-tin, the material loses its integrity: the grain structure dissolves and tin powder is produced.
The tendency towards conversion increases with decreasing temperature , but the reaction rate becomes slower . The ideal transition temperature is around −48 ° C. The transformation can be accelerated by alloying with other metals (e.g. zinc , aluminum ) or prevented (e.g. antimony , bismuth ). Contact with an alcoholic solution of pink salt ( ammonium hexachlorostannate , (NH 4 ) 2 [SnCl 6 ]) also accelerates the conversion.
Examples
- Many organ pipes in the visible area ( prospectus ) are made of an alloy with a high tin content for optical reasons and are particularly susceptible to tin plague.
- On the Russian campaign in 1812 by Napoleon the buttons of made of tin fell apart reportedly uniforms of his soldiers because of the cold.
- Also tin figures are - threatened the inexorable decay within a few months following infection by the tin pest - depending on their quality.
Web links
Tin plague: converting β- to α-tin time-lapse video on www.youtube.com
Individual evidence
- ↑ a b Andrea Hartwig : Tin . In: Römpp Chemistry Lexicon . Thieme Verlag, as of February 2004.
- ↑ Cecil Adams: Where did we get the idea crazy people think they're Napoleon? Plus: Did tin disease contribute to Napoleon's defeat in Russia? In: The Strait Dope , May 2, 2008.
- ↑ Julia Littmann: New historical scene in the Zinnfigurenklause , badische-zeitung.de, June 1, 2012, accessed on November 28, 2015.