User Rank
Misunderstood Tin
shjacks45   10/18/2011 5:58:16 AM
1. Although steels are metastable at room temp it takes dry ice temperatures to induce phase change. "Tin pest" disease proceeds slowly at first at 10 centigrade. Im never saw any reference in military journals that Napoleon or his officers attributed loss of buttons as significant.

2. Group 5 and group 6 alloys: bismuth, antimony, arsenic, tellurium, selenium, etc.; accelerate tin pest. Copper, Silver, Cadmium, Indium etc. alloys reduce tin phase change. Copper and Silver as intermetallic compounds Cu3Sn and Ag3Sn. Lead does not not form a solution in solid Tin, so it does not prevent tin phase change. However 50:50 Pb:Sn will leave a Lead matrix behind.

4. Pure Tin was unlikely a button material as it was too soft to hold the coats closed. More likely a Pewter Tin-Antimony-Lead alloy.

4. Russians had a Tin coin few years back. They wrestled with the Tin pest problem.

5. Tin whisker formation is proportional to Tin content of solder. Tin-Lead Solder is usually reflowed which reduces surface stress but Bright Tin plating is not reflowed.

6. Although Lead causes neural issues in young mammals in infinitessimal amounts, Silver is much more toxic to adult humans.

Dave Palmer
User Rank
Thermodynamic stability and metastability
Dave Palmer   10/6/2011 4:36:51 PM
Karen, beta tin (white tin) is stable at room temperature, not metastable.  Alpha tin (gray tin) becomes the stable phase below about 56°F.  So below 56°F, beta tin is metastable - it is no longer the lowest energy state, but there is still an activation energy associated with the phase transformation.

I think the term you wanted to use is "allotropic," not "metastable."

It's interesting how non-committal Le Couteur is about the historical veracity of the "Napoleon's buttons" story, given that it's the title of her book (although the story itself is actually only mentioned briefly in the introduction).

When people talk about "pure tin" in electronics applications, they mean that it is 97% pure or more.  However, I believe this still leaves enough room for alloying additions (antimony, bismuth, or lead) to suppress alpha tin formation.

Partner Zone
Latest Analysis
The company says it anticipates high-definition video for home security and other uses will be the next mature technology integrated into the IoT domain, hence the introduction of its MatrixCam devkit.
Siemens and Georgia Institute of Technology are partnering to address limitations in the current additive manufacturing design-to-production chain in an applied research project as part of the federally backed America Makes program.
Most of the new 3D printers and 3D printing technologies in this crop are breaking some boundaries, whether it's build volume-per-dollar ratios, multimaterials printing techniques, or new materials types.
Check out these gifts that will make you the hero of your Secret Santa party.
Voting has closed on our 2015 Gadget Freak of the Year contest, but it is not game over yet for two competing projects.
Design News Webinar Series
11/10/2015 11:00 a.m. California / 2:00 p.m. New York
10/29/2015 11:00 a.m. California / 2:00 p.m. New York
10/20/2015 8:00 a.m. California / 11:00 a.m. New York
12/2/2015 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Jul 6 - 10, Building Raspberry Pi Controllers with Python
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2015 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service