Aluminum magnesium alloys are aluminum based alloys with anywhere from 0.5% to 13% magnesium. The addition of magnesium decreases the formability of the aluminum but allows for much better corrosion resistance. Hydronalium alloys are a subset family of these alloys that can have anywhere between 1% to 12% magnesium as well as small amounts of manganese (usually under 1%).
These alloys are most well known in Eastern Europe, having originated in Germany in the 1930s, and were widely used for shipbuilding in Poland. They are most well known for their resistance to seawater corrosion. Other applications include violin strings (in those variants ductile enough to be drawn into wire), luggage, and glasses frames (as shown above). Hydronalium alloys are also difficult to manufacture, specifically when it comes to casting, and as such are not relatively common.