Everything about Tin Pest totally explained
Tin pest is an
autocatalytic,
allotropic transformation of the element
tin, which causes deterioration of tin objects at low temperatures. Tin pest has also been called
tin disease, or
tin leprosy (
Lèpre d'étain).
It was observed in
medieval Europe that the
pipes of
church pipe organs were affected in cool climates. As soon as the tin began decomposing, the process sped up, and seemed to feed on itself.
The allotropic transformation
At 13.2 degrees
Celsius (about 56 degrees
Fahrenheit) and below, pure tin transforms from the (silvery, ductile)
allotrope of β-modification
white tin to brittle, α-modification
grey tin. Eventually it decomposes into powder, hence the name
tin pest.
The decomposition will
catalyze itself, which is why the reaction seems to speed up once it starts; the mere presence of tin pest leads to
more tin pest. Tin objects at low
temperatures will simply disintegrate.
Possible historical examples
Scott expedition to Antarctica
In
1910 British polar
explorer Robert Scott hoped to be the first to reach the
South Pole, but was beaten by
Norwegian explorer
Roald Amundsen. On foot, the expedition trudged through the frozen
deserts of the
Antarctic, making for caches of
food and
kerosene deposited on the way in. In early
1912, at the first cache, there was no kerosene; the cans —
soldered with tin — were empty. Members of the expedition later died in the cold and
blizzards, only eleven miles from a massive depot of supplies.
The cause of the empty tins is unknown. Some observers blame poor quality soldering, although tin cans over eighty years old have been discovered in Antarctic buildings with the soldering in good condition. In any case, the lack of kerosene was just one factor in the deaths. One source observes,
The likely cause of death for Scott's polar party was some combination of scurvy, gangrene, starvation, dehydration, and hypothermia.
Napoleon's buttons
The story is often told of
Napoleon's men freezing in the bitter Russian winter, their clothes falling apart as tin pest ate the buttons. Whether failing buttons were indeed a contributing factor in the failure of
the invasion remains disputed; critics of the theory point out that the tin used would have been quite impure and thus more tolerant of cold temperatures. Laboratory tests provide evidence that the time required for unalloyed tin to develop significant tin pest damage at lowered temperatures is about 18 months, which is more than twice the length of Napoleon's Russian campaign.
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Modern tin
Today tin casting and plating avoids tin pest. The tin is
alloyed with small amounts of
antimony or
bismuth, which prevent the decomposition.
Silver,
indium, and
lead have also been used.
Further Information
Get more info on 'Tin Pest'.
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