[rollei_list] Re: I'm back!

  • From: Don Williams <dwilli10@xxxxxxxxxxxxx>
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Thu, 06 Jul 2006 18:50:50 -0700

At 04:28 PM 7/6/2006 -0700, Keith wrote:

"Bi-metal?" Please explain, Don.

the only bi-metal I know is in a thermostat!  ;-)


Keith, time to expand your range of knowledge. Sounds like you missed the buildup of air power during WWII.

Look up alclad.  Jerry knows all about it.

From one website there is a definition:

Alclad Sheet - A composite sheet having , on both surfaces, a metallurgically bonded aluminium or aluminium alloy coating which is anodic to the core alloy to which it is bonded, thus electrolytically protecting the core alloy against corrosion. Alclad on-side sheet has been treated on one surface only.

Or, from a different company, have a look here:


alclad was used in the manufacture of WW2 aircraft to combing the strength of one aluminum alloy while protecting it from corrosion by coating it with another, softer alloy. Worked fine except where the edges were exposed. No problem if they were waxed or painted, and no problem for the duration of the war.

I have no idea whether alclad is in current use for non-composite aircraft now, but Jerry will know.

I think there have even been problems with cameras due to this effect, the first Nikonos I think is a good example when folks didn't properly care for them.

Finally, bi-metallic thermostats are not very accurate, but they are very cheap and that's why they are used in most low-end domestic products. You won't find them in an industrial system where fine temperature control is required.


Aluminium Sheet, Aluminum Sheet

Don Williams
La Jolla, CA

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