Low-Tech Weapons and Tools Underwater

[weby]

Originally Posted by Icelander

What non-magical methods are available to surface dwellers to produce tools and weapons that are worth trading to undersea races?
Metals will rust or corrode over time. Granted, even if a metal spearhead corrodes or rusts into uselessless within a year of hard use, that's still a an improvement over a coral spearhead that breaks the first time you hit bone while killing a whale or sea serpent.

What metals provide the optimum balance between corroding or rusting slowly underwater and having desirable properties compared to bone or coral?

It really depends on the actual knowledge level and the willingness to experiment and such. A lot of things that have to do with corrosion resistance first appeared in 1800s, but some of it came into widespread use only much later. As examples cathodic protection system in test use from early 1800s (tl5) and chromium steels first noted to be better at resisting things in early 1800s(tl5), but first almost stainless steels from late 1800s(tl6) in their first appearances, but making the things to be actual products will require experimentation. Both ideas took more than 100 years from the first tests to wider use in real life.

Note that in terms of saltwater resistance of steels at least corrosion tends to be the bigger problem and rust a lesser(but significant).

Is there a meaningful difference between the durability of copper, brass or armour- (or weapon-) grade bronze under water? Does steel last longer than bronze or does rust ruin items faster than corrosion? Is steel better or worse than wrought iron?

Different alloys make a lot of difference, so a bit depending on your technology, but most metals actually tend to survive a while in water.

I do not know about bronze, but the copper sheathing proved fairly long lasting in ships (though as the corrosion process was not understood, the iron bolts had significant corrosion issues on the early experiments). Copper has a self protecting feature from corrosion where a less reactive surface forms protecting from corrosion. Iron does not form such (at least to a significant degree).

And if you have a sacrificial anode to corrode away the corrosion is reduced to a small fraction.
"You need to buy these magic iron talismans to fasten to your copper spear so it lasts longer"
"You need to buy these magic zinc talismans to fasten to your steel spear so it lasts longer"
All without any magic...

Are there non-magical alloys possible with TL4 technology that would be worth the extra trouble of making them, in terms of durability and quality?

Not really.

What about TL4+1 metallurgy, provided with a dormant volcano enchanted with a system for trapping magical fire, melting metals, mixing them and purifying? Research might yield TL4+2 metallurgy from that magic.

A lot of it depends on what your +1 means in terms of divergence.

If you have the ability to create very low carbon steel and have chrome available you may be able to create an alloy with enough chrome to be a proper stainless steel. Historically it was not until the aluminothermic(spelling?) reduction process for producing carbon-free chromium appeared just before 1900 that it could be done.

How hard is it to make stainless steel if you have the Measurement spell, high skill at Metallurgy/TL4+1 and a way to melt iron down to liquid form?

It really is a question of knowing how to make chromium alloys of iron. The hard part getting the carbon content low enough (and of course to know that you need to do that).

A lot of the things finally making "proper" stainless steel reality came from other TL6 developments and like most other science was a collaborative effort where one scientist discovers one thing and some other something else based on that.

So depending on the cinematic level of you campaign(Ie. how close to quick gadgeter do you want to go), you should judge the probability of a single person coming up with all the needed parts.