I'm in the planning process of a new pirate campaign for my players and rust is mentioned in the flavor for several weapons in the Pirates of the Inner Sea . I looked and asked on the boards, but it seems that there is no existing mechanic for natural rust of weapons. How would I go about adding some rules in for the rusting?
I read up on rust a little bit and found the following variables if they help.
-Alloys resist rusting such as steel which will be what virtually all weapons are made of.
-Seawater, acid rain, and snow belts speed the process of rusting due to the presence of better electrolytes.
-Water tends to have a higher percentage of oxygen than air and so it makes objects rust faster than air itself.
-The larger the exposed surface area the faster it will rust.
-Separation of oxygen from the object to be rusted is effective in preventing it such as certain oils.
-The hotter it is, the faster it will rust.
So any tips on putting in rules for rust? I think that I'll allow magic weapons a save against rusting (Fort) with a low DC (12?).
Basically a whet stone to remove the rust and daily oiling of a weapon should remove most of the chance of rust. An oiled leather sheathwould help as well.
Snow Belts generally rust faster cuz they salt the roads.
Magic weapons should be immune to natural rust...Mithril while it acts as silver, should be immune to tarnishing and Adamantine, yeah prolly immune as well.
Some points:
Not all steel resists rust. In general steel made of a certain alloy called "stainless steel" resists rust (using chromium in the alloy). To be effective against rust you have to use at least 10% chromium, which greatly reduces the strength of the metal. That's why battle weapons are made of high carbon steel, which rusts quite readily. So if you want to have effective weapons, then you have to keep them dry and oiled. In the real world on ships at sea sailors did not carry stainless steel weapons, they took care of the weapons they had.
For gaming purposes if someone wanted to use a "rust resistant" stainless steel sword, I would probably rule that it had a -1 at least to hit and damage, and that it would be fairly easy to sunder. I would do similar rules for stainless steel armor or shields.
Magic weapons and armor should be impervious to rust.
Saltwater does indeed greatly increase rust. As do other impurities in the water, but salt is a really good rust enhancer. Rust is also enhanced by proximity to other electrically active items, such as other rusting metal objects.
I'm not sure where you get the idea that water has a higher percentage of oxygen than air. Air is almost 1/4 oxygen. That's a lot of oxygen. If water had that much oxygen dissolved in it, it would explode when exposed to normal atmospheric pressures. The reason water increases rusting is because the water molecules themselves contribute to the reaction. The most common form of rust requires both molecular oxygen and water. Pure water won't rust iron that much, neither will pure oxygen.
Again, for gaming purposes, I would probably exaggerate rust so that it could have a game impact. You can always say it's not earth and things just rust faster in your world. I would allow for the existence of anti-rust spells which can protect weapons and armor from rust for up to one day per level of the caster as a first level spell.
Bronze doesn't rust, and is pretty strong, comparable to stainless steel, so you could have bronze weapons and armor be fairly common since it's a whole lot cheaper and easier to make than steel, and in this case, nearly as good. Brass would also be very common. (Bronze is an allow of copper and tin, brass is an alloy of copper and zinc. Zinc and tin are very common metals. "Galvanized" steel is essentially steel electro-plated with or dipped into zinc.)
You might allow for the creation of spells which accelerate rust. A rusted sword or armor could perhaps be fixed with the "mending" spell. Spells which remove oil or convert oil to saltwater could be cast surreptitiously on PCs weapons or armor, so that they could rust overnight.
Electrical activity accelerates rust. You can see this on steel or iron poles where electric currents either from electrical power or from natural electrical activity creates rust at a much faster rate than the iron or steel not exposed to the current. You could rule that spells like shocking grasp accelerate rust.
Not sure how far you want to go with this. Or why. But it could be an interesting campaign if done cleverly.
like x weeks of improper matanance the weapon get the broken quality. after another such x set of weeks its gets destroyed.
A lot of good ideas and a lot to think about, thanks for the ideas everyone, and adamantine dragon all of the talk of different alloys helped greatly.
For gaming purposes if someone wanted to use a "rust resistant" stainless steel sword, I would probably rule that it had a -1 at least to hit and damage, and that it would be fairly easy to sunder. I would do similar rules for stainless steel armor or shields.
The "Fragile" quality from Ultimate Combat is probably pretty good for this instead. It essentially gives you a pseudo-sundering situation all the time, and is pretty easy to repair if you have patience or magic. Masterwork and magical items don't suffer the penalties of the Fragile quality, and bronze items have Fragile already.
The penalty would be a bit hard to defend when the material is still a good deal harder than wood or stone, but wooden and stone weapons (arrows, javelins, obsidian daggers, clubs) don't take similar penalties in the rest of the rules.
Another angle to play up rust as a thematic element is to have other things like locks, door hinges, or chains in the environment rust. Sneaking in a poorly-maintained keep or guard post somewhere gets harder when door hinges squeak and locks are significantly harder to open. Makes silence spells more valuable, or perhaps the cantrip "mending" quite useful if it can undo rust (perhaps reduce the skill penalty by 1d4 per casting, but be aware of the weight/volume limit on it). Rusted chains might force two Climb checks or they break, causing you to fall- or they might be handy for opening things, like in so many video games.
Rusted weapons being used by undead, savage demi-humans, or just plain sadistic sentients might cause extra pain or even disease. It might also heighten the DC of Heal checks if your group makes frequent use of the skill, for having to clean the wound well or pull small broken bits out first. Rusty caltrops, anyone?
Great ideas, a lot of help with the aesthetics and really adds a bit of atmosphere to the old abandoned treasure. I am sure to use a few of these thanks for the ideas.
Water doesn't have oxygen dissolved in it, but water is primarily oxygen. (Of course, that's pure water, but that's beside the point.) Its the polarity of the water / salt / whatever that enables it to bond to the molecules of metal to create iron oxide, aka. rust.
Water doesn't have oxygen dissolved in it...? Water is primarily oxygen...? I hope I'm misunderstanding you.
I'm not sure where you get the idea that water has a higher percentage of oxygen than air. Air is almost 1/4 oxygen. That's a lot of oxygen. If water had that much oxygen dissolved in it, it would explode when exposed to normal atmospheric pressures. The reason water increases rusting is because the water molecules themselves contribute to the reaction. The most common form of rust requires both molecular oxygen and water. Pure water won't rust iron that much, neither will pure oxygen.Water doesn't have oxygen dissolved in it, but water is primarily oxygen. (Of course, that's pure water, but that's beside the point.) Its the polarity of the water / salt / whatever that enables it to bond to the molecules of metal to create iron oxide, aka. rust.
Oiling the weapon would work well to protect it, as would painting it. Of course, both would have to be maintained depending on how the weapon is handled.
Is it even worth the effort to educate you about water, oxygen and how they work?
Nah... it's not worth it...
It does not really matter to the game exactly why it happens that way, thats just the way it goes.