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Author Topic: Why was zinc used in iceboxes?  (Read 1750 times)

Offline thedoc

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Why was zinc used in iceboxes?
« on: 05/10/2015 10:50:01 »
Paul asked the Naked Scientists:
   In years gone by, why did they use zinc for iceboxes? When I was a lad my father used to suspend a zinc crate from tree branch over the stream as we did not have a fridge as folks do these days. I used to think that maybe my father had just knocked up the crate from someone's rubbish and that was why it was made of zinc.
Last night I tried googling "icebox" and "zinc" and I see zinc was used in iceboxes, but what I read did not tell me why. Was it just that it was thought to be less likely to corrode? I cannot remember if we had ants climbing down the rope to the zinc crate. Might insects be repelled by zinc? I'll have o google that.
What do you think?
« Last Edit: 05/10/2015 10:50:01 by _system »


 

Offline alysdexia

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Re: Why was zinc used in iceboxes?
« Reply #1 on: 09/01/2016 21:14:35 »
I'd say it was a corrosion barrier to dissolved salts, as pure zinc on boats serves as a sacrificial anode, but then why didn't they simply paint over it or enamel it?
 

Offline Ernie Paulson

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Re: Why was zinc used in iceboxes?
« Reply #2 on: 16/02/2016 04:57:39 »
Pretty sure the zinc was used just as a protective coating to prevent rusting. "Tinning" the steel box would provide a much better barrier for the steel than a coat of paint.
 

Offline chris

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Re: Why was zinc used in iceboxes?
« Reply #3 on: 16/02/2016 09:31:37 »
I think Ernie is right; zinc would have offered the best corrosion resistance, although not necessarily the best health outcome.
 

Offline SeanB

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Re: Why was zinc used in iceboxes?
« Reply #4 on: 16/02/2016 16:41:18 »
Zinc coated steel is both cheap, long lasting and above all very easy to work. The zinc coat is applied to the bare sheet before any forming operations, and as it is a sacrificial coat along with being a barrier by it forming a relatively inert oxide it is going to last a long time even if you keep denting it like will happen in putting a heavy load of ice in it or pulling bottles on the surface.

A paint coat or an enamelled coat both need application after finished forming, and they both have a problem in that any defect in the surface( a pinhole in the coat, a chip through it or a stress applied that cracks the coat) will create an electrochemical cell in contact with water and oxygen, causing corrosion of the underlying steel and a rapidly spreading rust spot that soon becomes a hole.

A zinc coat on the other hand protects the exposed steel for a long time till all the local zinc has been dissolved, which means a long lifetime. You could make the ice box out of something that resists corrosion, like stainless steels or copper, but both are very expensive in comparison to steel, and harder to work. Modern units use aluminium as it will self form a very hard oxide coat to provide the protection, but only recently has aluminium become cheap enough that it is comparable in cost to galvanised steel, or at least only around 5 times the price by mass.
 

Offline Colin2B

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Re: Why was zinc used in iceboxes?
« Reply #5 on: 16/02/2016 17:40:47 »
I remember in my grandmother's house sheet zinc was used  for food containers, meat safes, perforated zinc to keep out flies etc. I think as well as corrosion resistance it is a soft easy to work metal so forming boxes from sheet was easy.
 

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Re: Why was zinc used in iceboxes?
« Reply #5 on: 16/02/2016 17:40:47 »

 

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