There are a lot of good suggestions in this thread. Having said that, I
think it is unlikely you will be truly successful making something that
will last 500 years if you just get a bunch of opinions and don't spend
any further effort on it. At minimum, you need to do a bunch of research
to find out what applicable work has been published. I'll be so bold to
suggest you might actually want to do some accelerated aging tests on
sample containers.

The shell material is one issue. Two others are seals and environment.
You've mentioned seals--again, how in the world do you know your seal
material will last 500 years (more research needed...)? How do you
know it will be indoors all that time? Will the building last 500 years?
If you really expect 500 years out of it, you need to protect against
the possibility it won't be indoors.

There was a new motel going up near work about 10 years ago. The
building frame and walls were up (no exterior finish yet, insulation
hanging out), lots of window holes, many covered with plywood, looked
pretty ratty. My friend Phil says "Just think, in 100 years, it will
look exactly the same".

Steve



James wrote:

What commonly available alloy has the best corrorsion resistance
properties?

I am building a chamber that needs to last 500 years. It will be
indoors, but I need it to resist the effects of time and the elements.
I added commonly because I cannot afford some rare exotic metal.

Also, can anyone recommend a good metal rod, tube manufacter that
supplys their wares in metric sizes? (US based)

Thanks.