Metals (and alloys) have a high surface free energy (SFE), mostly > 1 J/m2. This means that water spreads, i.e. the contact angle is about 0°. 

Due to the high SFE substances from the surrounding atmosphere readily adsorb and form a well adhering layer of adsorbates. If the surface is exposed to normal atmosphere this kind of layer contains water, carbon dioxide, and hydrocarbons. The latter are responsible for a dramatic reduction of the SFE to values in the range of 20-40 mJ/ m2. In that case the water contact angle is usually in the range of 40° - 60°.

Since water droplets "sense" a layer of < 1 nm a very shallow layer is sufficient for this effect. The adsorbates are quite difficult to remove from such high SFE surfaces like metals. Vacuum only does not suffice. It takes additional measures like heat, UV radiation, plasma, or ... an ion beam.

In addition to the above, one should add that when depositing the alloy the composition of the film surface is generally not equal to the stoichiometric composition. But more important - when freshly deposited metal film is in contact with air atmosphere the oxide film instantly grows on its surface. So the airborn oxide would determine the hydrophilic or hydrophobic properties of the surface.

Thank you Alexander for your addition! You are completely right.

The SFE of oxides is usually in the order of several 100 J/ m2 and can be also > 1000 J/ m2. The adsorption properties are quite similar to those I described in my last comment.

In a quick google I found the paper from the Metalurgical Transaction on the SFE of copper and copper oxides

http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CDQQFjAB&url=http%3A%2F%2Flink.springer.com%2Fcontent%2Fpdf%2F10.1007%252FBF02644042.pdf&ei=w_rmVO-ODOO_ywPA54LwBg&usg=AFQjCNEmOFRynrx-mTXGHyoqgqq1Pw9efA