As any good metallurgist will tell you, you can't just take any two types of metal and weld them together. You may instead be able to just join them together with glue, however, thanks to research being carried out at Germany's Kiel University. Scientists there have developed an electro-chemical etching process that not only allows different metals to be strongly bonded to one another, but that also lets metal be bonded to almost any other material.
The "nanoscale-sculpturing" process only affects the very outer surface the metal – a layer that's about one quarter the thickness of the width of a human hair. The structure and stability of the metal beneath that layer remains unaltered.
Once treated, that outer layer takes on a dull matte appearance that's visible to the human eye. Viewed under a microscope, however, it's actually a three-dimensional landscape composed of tiny hooks. When two of these nano-sculptured surfaces are pressed together, with a bonding polymer applied between them, their hooks interlock with one another in three dimensions. From there, once the polymer sets, that bond reportedly becomes virtually unbreakable.
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Even the presence of contaminants such as fingerprint oil or gearbox oil apparently don't affect the strength of the connection. As a side benefit, the etching process makes metal surfaces water-repellant.
Additionally, the treatment can be used to remove less chemically-stable particles from metal surfaces. Medical implants, for instance, are often made from titanium with added aluminum – unfortunately, aluminum can cause adverse reactions in the body. Using the nanoscale-sculpturing process, however, most of the aluminum can be removed from the outer surface of the implant, lessening the likelihood of such complications.
Source: Kiel University