Instructables

Soda Can Hydrogen Generator for Alternative Energy

Step 5: UPDATE


Ironsmiter turned my attention to the fact that transporting mercury in aircraft was a danger to their aluminum structure. He referred to a pop-sci article titled "The Amazing Rusting Aluminum". Apparently mercury can "rust" aluminum in a few hour.

So i decide to test if the same happens with liquid metal.

I placed a drop on the bottom of the soda can and left it in the open air. It made a little grey fuzz on it's surface. Nothing spectacular happened, unlike mercury. That was two days ago.

I inspected the drop today and I COULD NOT FIND IT! IT LOOKED LIKE IT DRIED UP! Metal drying up, go figure! but there was a large blotch on the aluminum.

I added a little bit of water and the thing went INSANE! It bubbled like a volcano. There was so much heat the water dried up!

The reaction was much more violent then freshly applied liquid metal!
 
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DrStoooopid6 years ago
You let it set long enough for the liquid metal to penetrate the aluminium, thus accounting for the violent reaction, as there wasn't a way for their any oxidation to occur, because the liquid metal thoroughly "wetted" the aluminium. You should be able to recover your gallium from that dried up mess on top there, just like normal.
Biotele (author)  DrStoooopid6 years ago
Have you ever came across a reaction were a metal permeates another metal like it was a sponge? If you look carefully in the second picture, the liquid metals does not wet and spread on the surface, but actually mixes with the aluminum giving a different shine from the original aluminum. Yes the gallium is recoverable after the reaction.
How so?
that's what true wetting is...the liquid metal soaks into the other metal. That's supposed to happen. It didn't happen before because you didn't let it sit long enough before.
Biotele (author)  DrStoooopid6 years ago
I am not expert on metal on metal interaction, do you have some papers that describes this phenomena? Personally, I never heard of metal soaking into other metals. I thought wetting process involved the loss of surface tension in the liquid metal because of surface boundary amalgamation.
The byproduct of the reaction in step 5 looks very similar to the byproduct of a thermite reaction. I wonder if the aluminum is reacting with oxygen in the gallium mixture and the thermite reaction was hot enough to flash evaporate the water. However I don't know what caused the ignition.
Biotele (author)  Mechanical Engineer6 years ago
It is aluminum oxide just like in the thermite reaction. It is grey because it is mixed with the liquid metal. I recovered the aluminum oxide and added NaOH, The liquid metal precipitated leaving behind the white aluminum oxide like in the picture of step 4.
I am going to try this expirement in a dark room to determine if sparks or flame are present during the reaction I'll let you know what happens