How feasible would mass scale metallurgy be for a post-apocalyptic civilization?

Question

Let's assume that civilization is a total loss so after the initial die-off humanity has to rebuild itself from the hunter-gatherer stage. In a particularly harsh environment it may take a few thousand years to stabilize and then progress through the agricultural revolution, early civilization, and into metallurgy. During all this time the ruins of our technology would have been buried, scattered, or exposed to the elements, and all knowledge of how to exploit it lost.

As this answer suggests, a second industrial revolution wouldn't be viable because we've already cleaned out the requisite minerals that can be excavated without advanced technology. I wonder at what point non-renewable resources would be too inaccessible for technology to advance.

Would it even be likely that a successor civilization could develop widespread bronze and iron working? Would there be enough accessible metals and ores for smithing to catch on and lead to advancements? By that time would it be practical to scavenge from our ancient ruins, or would any usable alloys have rusted away? Is there any other path to a new iron age?

Answer 1

Not as easy as all that.

I disagree with @Catprog and @o.m. - especially given the time-frame.

A lot of material is going to get taken out to sea via weathering processes since it's now exposed on surface (and if metal is correlated with humans, most of it is near the sea: In America it's 39% of the population). Most of the ocean stuff will have washed away in hurricanes, global warming, etc, etc. eg: NYC without pumping running ends up underwater / subsiding. Anything that gets dissolved / taken to the sea will precipitate out of solution... onto the ocean floor. You'll then have to wait for it to go through the subduction zone and then recycled up into ores. That'll take a minute.

For an example, where is all of the gold, bronze, etc that was mined in ancient times? King Midas was a thing, since he had a mountain of gold ore. It got worn away, since the West used it in coinage.

Or, put it this way, how many garbage dumps from pre-Roman times have metal in them? Or even Roman midden-heaps?

Over thousands of years (or, heck, hundreds) most metals will be scavenged by primitives and used for knives, etc. Worn out and discarded. We don't have any bulk metal from civilizations that're as old as your proposed timeline.

Bronze was never easy (nor cheap), and required some world-wide trade routes to get at the tin necessary. It was too expensive for most of the things that needed to get done. How much tin do you expect to find in a garbage heap? How much tin (or bronze) is in your house right now?

Any of the stuff left isn't going to be that pure, most of it will be oxidized, or perhaps reacted with acid rain, or other by-products. You're going to have to figure out how to run smelting to get at pure materials. You can do it with charcoal, but you'll need forests* (4 to 1) in the right places. You won't be shipping anything by rail, without huge iron deposits to make those rails with - which means any 'garbage mines' will have to be by a river, ocean, or canal, or will have to be located in a forest.

Anything that's corroded, oxidized, or contaminated can be worse than some of the ores we've had. Granted, some of the ores we have had, and used, are exactly that (oxidized metal) - but they're often not the best ones.

All of these would make metals even more expensive than they were historically. Maybe much more. Which means you're not going to be doing a ton of experimenting with them. Nor making experimental devices that blow up out of your (equivalent of gold-reserves). The more expensive something is, the less likely you are to experiment with it.

• How're you going to have trees/forests? If you have a catastrophe, you're going to have to wipe out enough humans that they don't burn down all the trees for warmth when the first winter hits that they don't have industrialized society to run their heating for winter. If they haven't already cut them down to cook their food. And they'll need to not be wiping out the remaining trees when they harvest for next winter, and not wiping out those remaining trees for next winter... until you can get new growth to mature enough to be reproducing (and outpacing new human growth, and survivor's attempts at restarting industrial civilization).

Answer 2

Metallurgy would re-develop relatively quickly.

After an apocalypse, even if all the useful technology is gone, humanity wouldn't fall back to anything beyond 1700-ish technology. That is because all the very basic inventions - wheels, pulleys, irrigation, the concept of a printing press, even the basics of electricity - are already known and would not be forgotten. The amount of knowledge and basic scientific understanding in the heads of a group of survivors, yes even modern spoiled suburbanites, would surpass any group of scientists from 300 years ago, even if they could not immediately do anything with that knowledge.

People who survive and procreate would raise their children. Those children would speak in a modern, developed language. They'd learn about the past. They'd almost certainly be able to read and write. They would already know that you can melt metal and make useful things out if it. They would already know you can use coal in furnaces to create steel. All they have to do is start trying.

As for the resources themselves, there is no shortage of iron on Earth. Copper might be harder to find, but then the massive quantities we need in the modern world would not be needed by the survivors.

Answer 3

The iron in a single wrecked/buried/rusted steelworks would last an iron age town for centuries. Combine that with charcoal and you have the starting of metallurgy.

Answer 4

I'm going to add a bit to user3082's answer...

Availability

Old metals in their purified form: This is going to depend heavily on the types of metal, where they are and the conditions in your post-apocalyptic world. We have all kinds of metal that will last for eons if the worst they get exposed to is just the weather. This includes all metals and alloys that are either rather noble (gold, silver, copper) or that create protective layers (aluminum, stainless steel, ...). However, in other conditions they may just as well corrode rather fast (f.e. seawater tends to be pretty corrosive). Iron encased in concrete will also corrode rather slowly (potentially slowly enough to still be mostly there under a layer of rust after 1000 years). You may also find a lot of metal encased in plastic. Stupid example: bendable plumbing pipes that are made of aluminum that is encased in plastic on the inside and the outside. I assume your best chances are finding it buried somewhere or in a form that isn't otherwise easily exploitable by people just passing by.

Rusted metal: The metals that do rust will basically turn back into their original ores for the most part (that was the stable configuration they were found in, they will revert to it). Noble metals like gold and silver tend to remain pure (as they are found in nature as well, especially gold). The problem you may have is that they all spread and you can only find traces of ore in otherwise useless material.

There is still ore left, but it's going to be more limited than what we got the first try. We've been mining ore for quite a while now and we obviously started with the ores we could process first. There is probably still a lot of aluminum ore left (one of the most abundant elements in the earth's crust), but it's rather hard to refine for a low-tech civilization. Other ores (like iron, copper and tin) are probably going to be more of a problem (except for rather poor ores that can still be found everywhere). Scavenging what's left of them might be by far the easier and more economic option.

Metal processing technology

First requirement is heat for melting. This depends a lot on the metal. It can go from temperatures in the range of 400 - 800 celcius for the softer metals (aluminum, copper, ...) to closer to 2000 celcius for iron. So some could be melted using a well made wood oven, others need a little bit more. Second requirement is purity. Impurities in your starting materials have a lot of impact on the quality of the eventual result. For example steel is just purified iron. You can make do with impure metals to a certain extent (we worked with impure iron for hundreds of years), but it does have an impact. The tribes with purer metal will have superior weapons.

Post apocalyptic metalworking

I think their metal working would start again with metals like copper and aluminum. They both have low melting temperatures and tend to not corrode easily. This doesn't mean they will be in pristine conditions. They will probably have lost some material due to local corrosive conditions (see crevice corrosion, it's on wikipedia), but they wouldn't corrode in normal outside conditions. They would probably be able to scavenge some steel (and iron-alloys) that are not corroded away and use those straight away. For pure steel and iron, this is going to be rather limited. Alloys like stainless steel may stand a better chance (depending on the exact alloy), but they bring other problems such as: different (higher) melting temperature, need for specific ways of processing (you can't just weld stainless steels without messing up their properties).

So as you wish, iron technology would be rather rare. This may cause iron melting to be developed rather slowly or not at all (and steel production would be even more slowly or not at all). This means that the people that manage to scavenge iron or steel and don't fail at reprocessing could have some interesting advantages. Expect that most steel will turn into basic cast iron as they try to melt it (carbon from ash or burning materials will change the composition). The same problem will cause most iron alloys to fail and basically turn into something similar to cast iron.

Answer 5

Garbage dumps would be a large source of metal. (not just ore but actual metal, rusted perhaps). And probably in higher concentrations then the original mines.

http://en.wikipedia.org/wiki/Landfill_mining http://www.theguardian.com/business/2010/oct/11/energy-industry-landfill

And with the thousands of years the toxicity would have leached out and broken down.

For coal it would depend on the Apocalypse. Large scale flooding of the forests is how coal was made originally.

Answer 6

It would be very difficult for a post-apocalyptic civilization to rediscover metallurgy. As others have stated, the raw materials necessary for industrial scale production of iron (or any other metals) probably wouldn't exist in their world.

At one time in our distant past, there was an abundance of raw materials available. It wouldn't be uncommon to find a large gold nugget, or a diamond lying on the ground.

Now we must go through extraordinary measures to retrieve these resources. The vast majority of what is found today comes from mines deep within the Earth. Some of these mines are thousands of feet deep.

These people may still be able to find commonly elements such as iron in shallow mines. The rarer and more valuable elements may be completely unknown to them. It would be unlikely they would have access to ancient (our) technology. Over the course of a thousand years, the vast majority of our cars, buildings, etc. would decay and be unrecognizable. It only takes a matter of decades for items made of iron or steel to completely rust away if they are left out in the elements.

It is feasible that these people could go for tens of thousands of years and not progress further than being a hunter-gatherer society. It took thousands of years for our own society to prosper, and we had many more advantages.