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Hazards of Tin-Bismuth Alloy at High Temperature

When tin-bismuth (42:58 wt%)is heated to 400-450°C, is there a reaction and/or hazardous situation (i.e., toxic vapor, boiling)developed?

Dien Duong
chemicals nfgr - Houston, Texas
2006

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The temperature is far below the boiling points: Bi 1564°C, Sn 2625°C. From data in Smithells Metals Reference Book, 7th Edn., vapor pressures above this liquid are approximately 5.7 x10(E-15) atm bismuth and 4.5 x 10(E-17) atm tin. As this liquid is nearly thermodynamically ideal, the vapor is likely also ideal and hence, any intermetallic vapor formation is unlikely.

A possible risk is from oxidation in the presence of air/oxygen. Tin forms the fairly harmless SnO2 surface oxide. Bismuth can burn in air, emitting yellow Bi2O3 oxide fumes (m.p. 817°C). Cannot say if this will occur or be prevented by the liquid alloying or the surface oxide film. But if any is present, paraphrasing Frank Zappa, "Don't you breathe that yellow smoke."

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2006