AFAIU cold welding is like welding in that the two materials which were separate atomic matrices become one, as atoms from one 'object' do not care if their neighbours are from a different 'object', if they are close enough to be attracted to each other. It only works if the material does not have an oxide layer at it's surface, which is why it's been observed to happen in space (and apparently caused issues with joints no longer being able to move, or something like that).