Question

Would steel or aluminum be more suitable for a liquid oxygen container? Why?

Answer 1

Dear Student,

For long period storage of liquid oxygen, usually stainless steel containers are preferred.

The liquid oxygen is held in a stainless steel vessel surrounded by an outer exterior shells.

Between the inner vessel and outer shell is an insulation filled space in which vacuum is drawn.

These type of containers are known as Dewars, that means they are double-walled with a vacuum in the gap.  

The inner reservoir contains oxygen both as a liquid and gas.

Stainless steel is just a convenient material for the storage of liquid oxygen.

Corrosion-resistant, reasonably strong and tough, weld-able, bad thermal conductor, reasonably cheap, reflecting like a mirror are some of the properties of stainless steel.

Aluminum alloys would perhaps be an alternative.

But they couldn't be anodized to protect from wear and corrosion, because they would absorb and emit far infrared radiation and increase the loss of oxygen.

Aluminum alloys are also better thermal conductors and strong aluminum alloys are usually not weld-able without a heat treatment afterwards.

Easily weld-able alloys are often too soft.

Glass dewars were used for smaller quantities.

They are better insulators, but they are also a real hazard in the lab because they tend to implode and send glass shrapnel all around.

Hence, stainless steel is really an ideal choice for the storage of liquid oxygen.

Note:
The material has to be tough and strong *at the temperature of liquid oxygen*. That excludes a lot of steels, and selecting stainless steel should be done carefully. It should have a lot of nickel to stabilize the austenitic phase.