52005

Trying to design a structure that will corrode to collapse quickly  

April 27, 2009

My question is a bit complex. I am an architecture student in my last year at university and I'm looking for a metal that would literally start dissolving and breaking under normal/rainy weather conditions. I know that acid rain can accelerate the rate of corrosion or rust, however I was wondering which metal (which can be used architecturally) will dissolve (not sure if this is the right term) the fastest. The reason for this is that I would like my design to fall apart after a period of time, preferably a year or 2. The metal I'm looking for will be small and thin in size and will be used at the joints. I've done alot of research and most metals will create a surface to protect any further corrosion. This is not what I want. Any suggestions?

Lola Jacobs
Student - UK

Hi, Lola. Make the joints out of uncoated, unpainted steel. Accelerate the corrosion galvanically by making the panels out of copper, brass, or stainless steel. Just don't go and do any "State of Fear" demos of the hazards of acid rain :-)

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

First of all, I agree with Ted that I wouldn't like to think this was being used as some kind of demo for how corrosive rain is. Naturally occurring minerals can be far more corrosive; see, yellow stone park hot springs, which are extremely acidic

Secondly, unless I've skim read too much, you didn't state a time period for this thing to fall apart in, or the kinds of loads etc the joints will need to support in the rotting period.

I would suggest steel or iron, but I wouldn't leave it up to nature, I'd perhaps paint on some acidic solution to help accelerate the rotting, or go as far as wiring them up to a low voltage power supply to encourage the metal to rot in the damp.

Another option is something like aluminium. By coating it with something caustic, you can easily get that to dissolve. In fact, if you dissolve caustic soda in water until it no more will dissolve and then drop some tin foil it, it'll rot it so quickly the liquid can boil - depending on how much foil you add. It generates so much heat with loads of foil and lots of solution, the temperature rises really quick and pushes the reaction along exponentially, so it starts slow and then takes off into a boiling mess. You can dissolve an A4 sheet of foil in a minute or two this way.

If you're planning an artistic structure, you could construct it with aluminium joints and then go out and paint some caustic liquid on it every now and again. Potassium hydroxide - potash - will work even faster than sodium hydroxide.

But I doubt aluminium will give it the feel you're after if it has to have an artistic element to it. So you'll probably be better with steel.

I do like Ted's galvanic idea, but it may take quite a while without some help. My low voltage idea is basically the same but should allow more rapid results.

If you don't know anything about electrics, take advice on wiring it up. It won't be difficult and shouldn't be dangerous, it should only need a couple of volts on it; which is like wiring it to a pencil battery. But if the current is way too low, it won't help it rot much. A wall wart power plug may be enough depending on the size of it and time period.

Either way, I'd 100% have a barrier around said structure. The chemicals are too dirty to have kids dipping their fingers in, the power supply version (despite being extremely safe) is never something to allow the public around and then the final nail in the fence posts is the fact it's going to be structurally unsound.

John Heritage
- UK