Thatis interesting Roth, because I thought I had understood that most of the tin manufacturers had moves to Aluminum. Curious to know for sure. A quick google search turned this up:
"When iron rusts, it forms iron oxide—a reddish, powdery substance that quickly flakes off to expose fresh metal, which immediately begins to rust, and so on until your muffler falls off. But when aluminum rusts, it forms aluminum oxide, an entirely different animal. In crystal form, aluminum oxide is called corundum, sapphire or ruby (depending on the color), and it is among the hardest substances known. If you wanted to design a strong, scratchproof coating to put on a metal, few things other than diamond would be better than aluminum oxide. By rusting, aluminum is forming a protective coating that’s chemically identical to sapphire—transparent, impervious to air and many chemicals, and able to protect the surface from further rusting: As soon as a microscopically thin layer has formed, the rusting stops. (“Anodized” aluminum has been treated with acid and electricity to force it to grow an extra-thick layer of rust, because the more you have on the surface, the stronger and more scratch-resistant it is.)"