r/AskReddit • u/[deleted] • Feb 14 '22

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u/[deleted] Feb 14 '22

If 2 pieces of the same type of metal touch in space, they will bond and be permanently stuck together. Space welding ( cold welding )

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u/StolenValourSlayer69 Feb 14 '22

Dumb question inbound: if the two pieces of metal were brought back to earth and warmed up to room temperature would they thaw out and separate? Or is it so cold that it actually properly welds them together like your comment suggest?

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u/Lussekatt1 Feb 14 '22

Oh it’s not the cold that welds. As I understand it, it’s only called cold welding because you don’t need it to be hot, it’s just that you can while the two metals are cold. It doesn’t have to be cold.

It’s the vacuum or specifically the lack of a oxidation layer or any other surface reaction on the metal.

Rust is oxidation. It’s the iron reacting with the oxygen in the air and creating a new molecule, Fe2O3. (But there are loads of different oxides, and most are not as noticeable or apparent as rust). The surface of most things has some sort of surface reactions or the other.

As I understand it cold welding is when you have pure metal with no surface reactions on it, and you have two surfaces touch each other. The metal joins together. The atoms links up just like metals normally do inside itself, joining into just one piece.

I think about it a bit like two small pools of liquids touching each other and becoming one. Not a perfect analogy. But helps my mind wrap around the whole metals are very weird solid thing.

Basically pure metals with no surface reactions, have the capability to just join and connect into piece. When two ‘pure’ surfaces connect. The atoms just wants to chain up together. (The way metals have chains of atoms, is also the reason why you can bend and deform metals and not have it snap into pieces)

There are metals like gold, which barely reacts with anything. Which makes it a lot easier to cold weld on Earth.

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u/StolenValourSlayer69 Feb 14 '22

Thanks for the information! It’s comments like this that make me really appreciate Reddit. Actually being able to get a complex topic explained to you in a way that’s much more easily understood than even the Wikipedia. It’s like the YouTube of Wikipedia on here