Marine Applications of 5xxx Series Aluminum Alloys
The applications of the 5xxx series aluminum alloys range from shipping containers to their most prolific application, boats. Whether building a recreational boat, commercial ship, or naval vessel, the advantages that the 5xxx series of aluminum alloy have, make it the premier building material for anything marine related. Before we ‘dive’ into the specific advantages of the 5xxx series and it applications, lets break down what aluminum alloys are and what sets the 5xxx series apart.
What is an aluminum alloy and what does it mean when an alloy is considered part of the 5xxx series?
Simply, an aluminum alloy is created by adding elements to pure aluminum, creating a chemical composition that has enhanced properties (typically to increase strength). Once these compositions are created they are assigned a 4-digit number where the first digit signifies a general series that characterizes its main alloying elements. For the 5xxx series, its main agent is magnesium which gives the alloy high strength as well as good weld ability amongst other things.
What are the advantages of 5xxx aluminum alloys?
- Weight Saving: By using 5xxx aluminum alloy, structures save an average of 55 to 67% of their weight. With comparable strength to mild steel, the alloy’s ability to decrease a structures weight can be hugely beneficial, especially for marine vessels. By saving weight the boats can increase payload, haul more equipment, and lower the amount of power required to power the boat.
- Weld ability: With weld yield strengths of 100 to 200 MPa, the 5xxx series have good weld ductility without post weld heat treatments.
- Corrosion resistance: The 5xxx series has lower resistance to corrosion making it ideal for any structure that will be coming in contact with water or chemicals. Through a 10-year seawater test, the tensile strength of the alloy showed reductions of only 2 to 5%.
What are the marine applications of 5xxx Series Aluminum Alloys?
- Pleasure Boats: Made from both 5xxx and 6xxx series aluminum alloys, pleasure boats utilize the alloys ease of fabrication, corrosion resistance, and cost effectiveness for building their hull or other equipment.
- Commercial ships: Many passenger vessels utilize the 5xxx series for both superstructures and equipment; ranging from 1000 to 2000 tons per ship. Since for many ocean liners appearance is important, the structures are painted but aluminum allows for a 50% longer time frame till repainting.
- Naval Vessels: Each year, 6000 tons of aluminum is used on destroyers. Within the past decade, 5456 plate and extrusions have become the standard for the welded deckhouse structures of destroyers. The weight saving ability of the 5xxx series allows the ship to maintain stability with its narrow hull that is needed to reach high speeds. Beyond the main structure, the alloy can also be employed for a variety of equipment including doors, windows, gratings, lockers, bunks, etc.
It is the use of the aluminum alloys that has allowed the marine industry to undergo a technological revolution. While the aluminum may have an initial cost premium, its ability to create lighter ships with lower maintenance costs means that the ship will be a worthwhile investment over the course of its life. And though boats may not be the first thing you think of when discussing the application of an aluminum alloy, the 5xxx series aluminum alloy has transformed the marine industry for the better.