View Full Version : Quick Query...

2011-03-11, 06:04 PM
Ok, so, let's say we have a dragon who has around a ton (not the colloquial "a lot", but an actual measuring unit "ton") of iron ingots. He needs to store them somewhere, but sadly, he lives in a fairly small cave (rent on the big ones is just too expensive these days). But wait! He has access to a small cave lake, but sadly, his Knowledge (chemistry) score is low. He doesn't remember what will happen if he sinks iron ingots in a lake.

Will they corrode? It seems air is required for that, so if you just sink them all into the lake as a storage mechanism, they should be ok. But then again, shipwrecks seem to disagree. Can a confused dragon in dire need of storage space get some help?

tl;dr: Iron ingots in a lake. What happens?

2011-03-11, 06:10 PM
Water contains oxygen, usually diluted in the water. Fish breath this. The iron is gonna rust.

2011-03-11, 06:25 PM
Water contains oxygen, usually diluted in the water. Fish breath this. The iron is gonna rust.
Source I found said that iron in "pure" water is not going to corrode. I assume this means 100% H2O? If so, damn.

Any idea how quick a.. 5 lb iron ingot will corrode in, say, freshwater?

2011-03-11, 10:14 PM
I think you want to look at shipwrecks as a good source of real world examples of what will happen. My understanding is that the exterior will rust protecting the internal part of the bar from corroding very fast. Old cannons get dregged up from wrecks in the atlantic a lot and are basically in a condition where they have the potential to be restored with a lot of work. In freshwater the corrosion is slower since the salt content is lower. The great lakes have had their fair share of wrecks over the years, so there are sure to be plenty of examples (the Edmund Fitzgerald comes to mind). I don't remember for sure, but I feel that the iron cannons from great lake wrecks did rust over time, although I can't remember any examples specifically.

I find it hard to believe that iron in water won't corrode, since rust is just iron oxide and water is mostly oxygen (by mass).

Jack Squat
2011-03-11, 10:19 PM
from http://www.roscoemoss.com/tech_manuals/fmcf/

When water contains less iron than the maximum that it is capable of carrying in solution, it corrodes iron or steel rapidly - unless a protective film or crust of some material covers the metal surface. The unsaturated water tends to dissolve metal from the surface of well screens, well casing or piping systems until it becomes saturated with respect to iron. If the mineral content of the water is such that a protective film is not formed by deposition of insoluble materials, severe corrosion results. [...]Corrosion in fresh water very often results in pitting so that, because of statistical variation in pit geometry, experiments under identical conditions will not yield identical results.

Generally, cold water causes corrosion to slow, but there's not really anything to be able to predict how long something will take to corrode, as it's not really repeatable.

2011-03-11, 10:30 PM
Good news! Solid iron is approximately 7850 kg per cubic meter. This is equal to about 8.65 tons per cubic meter. For 1 ton of iron, you need about .11 cubic meters. This is equal to a box of just a teensy bit more than 1m x .5m x .2m. Of course, we'll just suppose the dragon needs room for another coffee table and sink that anyway. Just get one of those vacuum seal plastic baggies, store inside, THEN sink it. Problem solved.

Of course, that doesn't answer the question you were probably trying to figure out, but it's good to keep in mind when storing iron by weight.