I need the effects of rust (and decay of other materials as well)

[Backfire]

So im working on a setting for a bunch of friends and decided to go with a classic medieval on top of old technology with a big theme of rust the further east the party travels but I'm not exactly a science boy so the most I know is tetanus is a thing and that iron is destroyed by it over time so if some of you smart science men could help me out it would be much appreciated.

So in short I need what it actually does to metal but also cloth, furs, leathers, the body, food, water, wood and anything else you can think of.

Thanks again this is my first post on here so please be underatanding if I have no idea how to use things.

You guys have opened my eyes so I'm going to make a little edit here for those who would like to add their input

If you think theirs other dangerous decaying metals or other materials for that matter that might be useful to look into please tell me I'd love to know what you think. This includes diseases that find their homes on these materials.

[Yora]

The main thing about rust is that it makes iron expand as it is rusting. This expansion causes the rusty surface to crack and flake off, exposing deeper layers of iron to air and water. This way a lump of iron and most steels will eventually rust all the way through and become a brittle powdery heap.

This is very different from oxidizing copper. When copper oxidizes it does not expand, so you just get a thin green coating on the surface and then it stops. Silver goes black in the same way and gold doesn't even do that. Rust really only affects iron. Stainless steel exist and it does not rust, but that's because it's mixed with chromium and put through a process that makes the chromium seal off the surface, similar to what happens in copper. But stainless steel is a quite recent invention and I don't think chromium is available with medieval technology.

[tyckspoon]

Rust is specifically a thing for iron - it's what happens when it reacts with oxygen. The resulting compound is rust. The reason it tends to destroy iron objects is rust itself is air-permeable, so it lets more oxygen through itself, resulting in previously unexposed iron encountering the oxygen, causing more rusting. It's also much more brittle and easily damaged than non-oxygenated iron, resulting in a weak spot in the item. Other materials can be oxidized by exposure to oxygen, resulting in bronze-oxygen, copper-oxygen, etc compounds (this is what the green coating that forms on copper items is) but most of these compounds form a stable, non-permeable barrier so the reaction doesn't spread further into the item.

So.. 'Rust' as a theme or concept doesn't make a lot of sense for anything other than iron and iron-derived items. Most things can potentially decay or break down faster, tho, if you want to use a general theme of 'nothing lasts as long here' - leather and cloth goods can suffer dry rot with very similar results to rusting (the material becomes fragile and easy to break apart) food and water may spoil faster as the micro-organisms responsible for spoilage grow more rapidly, people's skin dries out and is more likely to suffer scrapes, papercuts, and other minor injuries from handling things that wouldn't damage it normally.

[LordEntrails]

As mentioned, "rust" is the oxidation of iron. Oxidation of iron causes decay.

Assuming you mean "decay" of things, then what effects do you want it to have?

Leather and furs and many things decay differently based upon what is causing them to decay (mold, water, bacteria, drying, etc).

In general, decay causes things to break when exposed to forces/stress (i.e. use). So perhaps iron based armor might have a chance of breaking every time it is hit. Metal or wood weapons might fail (break, blowup, etc) each time they are used. Decayed furs and such might fall apart and become useless, but before that they might not provide the same level of warmth.

Something like a bowstring might be useless and have to be replaced.

Food could lose its nutritional value, decay to nothing or become poisonous. Or, might turn into something else, like vinegar, cheese, etc.

The body... decay of a body is normally what we call aging. So if the body was being magically decayed, then you could lose strength, constitution or other things we attribute to aging.

But, how this all is going to show up in game mechanics depends upon what game you are playing, and how you want it to be implemented.

[factotum]

Since no-one else mentioned it, the disease tetanus has nothing to do with rust. The bacteria that causes the infection may be more likely to be found on rusty iron than clean, but that's because of the dirt, not the rust.

[Backfire]

Rust is specifically a thing for iron - it's what happens when it reacts with oxygen. The resulting compound is rust. The reason it tends to destroy iron objects is rust itself is air-permeable, so it lets more oxygen through itself, resulting in previously unexposed iron encountering the oxygen, causing more rusting. It's also much more brittle and easily damaged than non-oxygenated iron, resulting in a weak spot in the item. Other materials can be oxidized by exposure to oxygen, resulting in bronze-oxygen, copper-oxygen, etc compounds (this is what the green coating that forms on copper items is) but most of these compounds form a stable, non-permeable barrier so the reaction doesn't spread further into the item.

So.. 'Rust' as a theme or concept doesn't make a lot of sense for anything other than iron and iron-derived items. Most things can potentially decay or break down faster, tho, if you want to use a general theme of 'nothing lasts as long here' - leather and cloth goods can suffer dry rot with very similar results to rusting (the material becomes fragile and easy to break apart) food and water may spoil faster as the micro-organisms responsible for spoilage grow more rapidly, people's skin dries out and is more likely to suffer scrapes, papercuts, and other minor injuries from handling things that wouldn't damage it normally.

Damn you guys are fast I just came to this page so I'd have it ready to refresh later. On to the topic at hand yeah its not the best concept for a theme but it was a halfbaked one that I have bassically just started working on so your input of nothing lasts long helps me flesh it out more for sure. I'm only sayed rust because im going off the idea that diseases and decay were often seen as curses of sorts and my first idea was changing the name of lock jaw to the Lock. But rust at least to me seemed to be more dangerous than other decaying metals due to its tendency to create jagged edges and host to tetanus. If you think theirs other dangerous decaying metals or other materials for that matter that might be useful to look into please tell me I'd love to know what you think.

[Manga Shoggoth]

If you mean the affect rust has on other things:

As already noted, rust expands, so a joint that is rusting will become stiff and eventually jam. Same things will happen with locks and so on.

Although rust won't directly degrade materials, it can stain them quite heavily.

In a salt environment things seem to rust more readily.

[Khedrac]

If I remember school chemistry correctly (it's been a while and things get updated too) rust is a reaction of iron and water and oxygen - it does need the water (the equation I was taught in school didn't even balance - the correct requirements apparantly were not known back then). One of the reasons things rust faster in salt conditions is that salt will absorb the water out of the air making whatever the salt is on wet - and hey presto you now have the 3rd component needed for rust....

The decay of most organic materials usually needs water too (without water the usual result is mummification, but 10,000-year old giant sloth skin was mistaken for being fresh). With organics simple decay is usually characterised by mould and mildew, but fabrics can also wear out/weaken through use and decay.

As for tetanus, clostridium tetani is an anerobic bacterium, so oxygen kills it, this is why tetanus infections tend only to arise from deep punctures that don't bleed much where the bacteria can transfer from the dirt to the flesh without being exposed to the air for very long.
For a medieval setting there are loads of other infections (bacteria, fungi etc.) that are probably more of a threat without magic healing - the basic rules was that any wound could kill (so a simple thorn to the thumb could give scepticemia and kill you) so polticies were important whether they worked or not. Broken limbs might not set properly but were much less dangerous if no blood was shed. Speaking of shedding blood, wounds that bleed freely are less likely to have dirt trapped in them (the blood washes it out) so are usually more survivable than those that don't. Gut wounds that puncture the intestine pretty much guarantee infection and death.

Welcome to the lottery.

[snowblizz]

If I remember school chemistry correctly (it's been a while and things get updated too) rust is a reaction of iron and water and oxygen - it does need the water (the equation I was taught in school didn't even balance - the correct requirements apparantly were not known back then). One of the reasons things rust faster in salt conditions is that salt will absorb the water out of the air making whatever the salt is on wet - and hey presto you now have the 3rd component needed for rust....
Not quite.

https://en.wikipedia.org/wiki/Rust

Salt acceleraes the process as electrolytes, very roughly speaking.


The decay of most organic materials usually needs water too (without water the usual result is mummification, but 10,000-year old giant sloth skin was mistaken for being fresh). With organics simple decay is usually characterised by mould and mildew, but fabrics can also wear out/weaken through use and decay.
It's not the water per se. It's all the things it carries. Organic material is preserved well in water in non-oxidizing conditions. It's various microorganism that does the most to break up organic material.

That's also why absence of water, ie dry conditions, gives good preservation. Organisms cannot grow and feast on the organic materials without water.

[Khedrac]

It's not the water per se. It's all the things it carries. Organic material is preserved well in water in non-oxidizing conditions. It's various microorganism that does the most to break up organic material.

That's also why absence of water, ie dry conditions, gives good preservation. Organisms cannot grow and feast on the organic materials without water.
Good point - the Black Sea has the dead zone with very little decay which is certainly not short of water!

[Fat Rooster]

As others have said, rust is a specific to iron thing, with the expansion causing flaking being a major factor in making it behave like it does. You are in a fantasy setting though, so simply making all other objects decay similarly is something you can do. Something about the air just causes everything to go brittle and flake, eventually crumbling completely to dust. Some mechanism for recycling the dust back to materials is required if you don't want the place to end up a desert though. Maybe rains that wash everything into a river that plunges into an abyss, through the elemental plane of earth and into the plane of fire, washing away any loose dust and exposing endless fresh material. Going up you end up in the gravity-less plane of air, with rivers running through it up to the plane of water. The rivers cause the rains. You can build inevitable decay into your cosmology.


One thing frequently missed about rust is how abrasive it is. Much of the time it is not rust that destroys machines so much as rust flaking off, and getting between bearing surfaces. As they bear against each other, the rust cuts grooves. Expect machines to randomly break the farther east you go, simply from the dust.

Edit: Actually, making everything behave like white tin (https://youtu.be/Q9zdt-rOB0Y?t=102) when exposed to air might be what you are looking for.

[Brother Oni]

Something like a bowstring might be useless and have to be replaced.

Note that a bowstring, or worse the bow itself or an arrow, snapping when its put under tension while drawing can cause injuries or even fatalities.

This is even more hazardous with crossbows which are under even greater tension - just the thought of the steel prod of a 500lb draw weight crossbow snapping makes me wince.

[snowblizz]

Good point - the Black Sea has the dead zone with very little decay which is certainly not short of water!

Yup. I was also thinking of the Baltic where a lot of wooden ships survive eg, since ther's no shipeaterworms.

And plenty of bogs up in the north yield organics in Ireland, north Germany and Scandinavia.

[Knaight]

The rust theme could be extended to oxidation in general, and while most forms of that are relatively innocuous there's several major exceptions. Most notable is burning, and in its slower form decomposition of organic matter into volatiles.

Most other metals will form just surface oxides. Some of these are at least more fragile, and could wear down from friction. Alkali metals and alkaline earth metals are a bit of an exception here. Alkali metals will generally go up in energetic flames pretty quickly (hence their storage in oils), alkaline earth metals are a lot more stable. Still, they'll generally burn pretty readily, and a pile of magnesium just lighting up in the background in the rust area is potentially fun.


If I remember school chemistry correctly (it's been a while and things get updated too) rust is a reaction of iron and water and oxygen - it does need the water (the equation I was taught in school didn't even balance - the correct requirements apparantly were not known back then). One of the reasons things rust faster in salt conditions is that salt will absorb the water out of the air making whatever the salt is on wet - and hey presto you now have the 3rd component needed for rust....


This is probably you not remembering it (or not understanding a shorthand notation that doesn't explicitly show everything) - the stoichiometry is exceedingly basic, and generalized methods for solving reaction stoichiometry far more complex than iron oxidation were pretty well developed long before anyone currently alive was in school.

[Algeh]

On a notably less scientific note, if this is a D&D game you should probably consider including rust monsters (http://www.d20srd.org/srd/monsters/rustMonster.htm), and possibly a variety of other monsters that behave similarly for other metals/substances. This can either be the cause of the area being so rusty or just a thing that is happening, but it's an old-school D&D thing you may want to consider adding given your theme.