"Tin Pest": Why Cold Tin Can Crumble Into Powder

Tin shows the most dramatic allotropic transformation of any metal covered in this series, a change in crystal structure so complete that the two forms barely resemble the same element mechanically.

β-Tin / White Tin, stable above 13.2°C · BCC unit cell · a = 5.830 ÅReal β-tin is body-centred tetragonal (a = 5.83 Å, c = 3.18 Å), not a perfect cube, this viewer shows the simple cubic BCC pattern as the closest available approximation; the real cell is stretched along one axis.Drag to rotate · scroll to zoom

α-Tin / Grey Tin, stable below 13.2°C · DIAMOND unit cell · a = 6.490 ÅThe same diamond cubic structure as silicon, covered on silicon's materials science page, just with a larger lattice parameter. Grey tin is brittle, dull, and distinctly non-metallic, a genuinely different material by feel.Drag to rotate · scroll to zoom

13.2°C

β (metallic) to α (grey) transition

Body-centred tetragonal

Real β-tin structure

not simple cubic

Diamond cubic

Real α-tin structure

same family as silicon, not a metal

Why this transformation is called a “pest”

Unlike cobalt’s HCP-to-FCC switch, covered on cobalt’s materials science page, which leaves cobalt metallic and useful in both forms, tin’s low-temperature alpha phase is brittle and non-metallic, diamond cubic is a covalently bonded semiconductor structure, not a metal’s. Tin objects held below 13.2°C for extended periods can, in genuine documented cases, slowly crumble as the transformation propagates, a real materials failure mode historically significant enough to earn its own name.

k = A\,e^{-E_a/RT}

The Arrhenius equation, the same rate law introduced on cobalt's and steel's materials science pages. The transformation is kinetically slow near 13.2°C, which is why tin pest is a real but comparatively rare practical problem, most tin alloys and most ordinary use temperatures do not sit in the range and timescale where it becomes significant.

Why alloying and impurities matter here too

Small amounts of certain impurities or alloying elements can suppress or accelerate the transformation, a real, documented effect that modern lead-free solders, covered on this material’s application-wise page, have had to account for specifically, since eliminating lead from solder alloys changed the tin-rich matrix’s own susceptibility to this transformation.

Sources: tin allotropy, transition temperature, and tin pest are standard, well-documented materials science facts (ASM Handbook); lattice parameters are standard crystallographic values.