Copper alloys are widely used in marine applications because of their resistance to corrosion, good machineability, as well as their thermal and electrical conductivity. Bronze alloys, in particular, are the preferred metal for casting large ship propellers.
Mecklenburger Metallguss GmbH (MMG) of Germany is considered a world leader in the design and production 
of propellers for large container ships.
In 2006, MMG produced the world's largest ship propeller for the Emma Maersk, which at 1,302 feet (397m) is one of the longest container ships ever constructed.
Emma Maersk's six-blade, single-piece propeller took one and a half years of development and planning, while the metal used to cast the propeller is an alloy of copper, aluminum, nickel, iron and manganese.
The propeller has a diameter of 9.6 meters and weighs over 130 tons. Because of its massive size, it required two weeks to cool after casting and then three weeks of milling before it was ready for delivery and installation.
More about copper alloys used in marine applications.
Image: The Emma Maersk propeller. Source: http://www.robse.dk/pages/Emma/ImagesReal.asp
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