Re: How good would Aluminum armor be?
 

Side note on low tech aluminium:

The process for extracting aluminium from clay is very energy intensive; but not actually using any metallurgical processes above TL2- it's just that no one thought to react bauxite clay with acid, boil off the result, melt in crucible the result of that. That knowledge could have allowed aluminium extraction at TL2ish where it would have been pretty competitive with copper and bronze as a tool/armour/weapon material.

Re: How good would Aluminum armor be?
 

The thing is that we need to be talking TL1-ish. TL2 is the Iron Age and copper and bronze have been reduced to specialty niches.

Re: How good would Aluminum armor be?
 

One reason the question comes up is for fantasy games. Those iron-vulnerable fae need something other than steel. And (as always) magic might substitute for technology.

Re: How good would Aluminum armor be?
 

Until TL6 electric furnaces, all previous methods of refining aluminum were very resource-intensive. The best TL5 was able to do was reduce the cost of aluminum from being more expensive than gold, to merely more expensive than silver. I'm no chemist, but even this appears to have required things like vacuums or pure elemental potassium that will be tough to pull off at TL2 (or if you can do it, you're no longer TL2 in any meaningful sense).

Re: How good would Aluminum armor be?
 

One curiosity to keep in mind with aluminum armor - aluminum reacts ... interestingly ... with elemental mercury. Exposure to mercury can result in even fairly large pieces of aluminum corroding away within hours.

Luke

Re: How good would Aluminum armor be?
 

Bronze. It's more expensive than iron, but it's perfectly good armor.

Re: How good would Aluminum armor be?
 

While your timeline is correct, the reasons are not exact. Aluminum was barely in the range of 'applied theroy' in the 1800s and would not be processed in any reasonable form until the mid 1850s. That processing method (dissolve bauxite clay in a mixture of acid, boil away results, collect aluminum powder) was actually viable (though not nearly as effective as the current electrolytic method) and would represent the drop from 'more expensive then gold and platinum' to 10% of that, it would require either instruction, or a compelling reason to try to isolate the metal inside clay (and knowing that there IS a metal inside clay) to do so at TL2, but there is nothing particularly complicated about the process (labour intensive, but not complicated).

Re: How good would Aluminum armor be?
 

The non-electrolysis process invented in the mid 1850s (Deville's modification of the Wöhler process) required metallic sodium. Metallic sodium was not isolated until 1807 -- via electrolysis (the Wöhler process used potassium, also isolated in 1807). Production of aluminum without electrolysis requires a stronger reducing agent than aluminum, and there are no alkali or alkaline earth metals that occur naturally (carbon can pull oxygen off of iron, but not off of aluminum).

Re: How good would Aluminum armor be?
 

Aluminum has an oxidation number of 3, there are stronger oxidizers (the Group IVA-VIIA metals). Are you saying that they don't occur naturally in any form that would be useable for this? I'm assuming that's the case, or I really don't understand oxidation-reduction (and I really thought I did).

Re: How good would Aluminum armor be?
 

You want reduction potential, not number (on that table, the top is strong oxidizers, the bottom is strong reducers). All of the stronger reducing agents are alkalines or alkaline earths, and do not occur in pure form in nature.