I'm writing a book set in a zombie apocalypse. It has been under this apocalypse so 50 years. Iron is one of the zombies' only weaknesses. Iron mining techniques at the time of the start of the apocalypse were similar to medieval iron mining techniques. The apocalypse has meant that no one is currently mining for iron (people prioritize surviving over mining) meaning that iron and its alloys are incredibly expensive. In this situation, what metals could the survivors use to substitute iron (used for tools, building, weaponry, transport etc.) instead of iron and iron alloys?
closed as too broad by Aify, Vincent, Brythan, Thucydides, bilbo_pingouin Jul 18 '16 at 7:02
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Probably the same metals we use every day other than iron. In other words, most of the natural periodic table (and even some trans-uranic elements)
Nickel, Cobalt and Chromium are quite similar to iron in many ways.
Aluminum is commonly used where lightness is an advantage.
You can find advantages to many other metals.
Iron would still be missed, the combination of abundance (cheap) and high-strength is the reason is it the preferred construction material in so many cases.
Biological iron could be a real problem in your world. Hemoglobin would not be possible, another compound cytochrome P-450 requires iron and is necessary in a variety of biologic functions.
Ruthenium would seem to be the natural choice as it is simply one row down on the period table, but it is far too rare to be a useful substitute in most cases. Only 20 tons of Rh are produced each year, mostly as a by production of platinum mining.
Alternatives: titanium, bronze, brass, carbon (as polymers, carbon fibre, graphene, CNT), silicon (as polymers, glass), tungsten, aluminium, copper, ceramics. All of them have advantages and disadvantages over iron alloys. Most of the above are costlier than iron alloys because of the cost of production or scarcity in the real world. But in your world iron is rare so they are good to go. Some of them are more brittle than iron (tungsten, ceramics, glass etc.) Some are softer (titanium, polymers, aluminium etc.) So they will replace iron in your world. They will be used according to their properties and as not a single one of them can replace iron completely, people will use all of them in conjunction.
Iron is an extremely common element; once humans know how to refine it from ore, it is going to be quite difficult for another species to really monopolise it. Doubly so for zombies, if they are the stereotypical kind of zombies that cannot plan anything in advance.
If the apocalypse is so bad that we actually lose the technology for refining iron from ore, I suppose that we still can resort to scrapyards; there should be a lot of iron and other useful metals there.
The only magnetic metals besides iron are nickel and cobalt, and I would fear that if we lose access to iron, we would with even more reason lose access to nickel and cobalt.
I think your plot idea is inconsistent, as it stands. One of the most common elements in the earth has become extremely rare (how?) so mining everywhere has stopped (why?). And as said above, if mining iron ore isn't possible how on earth will they mine metals rarer than iron? Anything mining rarer metal ores has a pretty good chance of turning up iron ore too.