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Uses for Aluminum Alloys in Boats

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The first thoughts many people have when they think about the industrial uses of aluminum alloys are often beverage cans or aircraft, two important examples of how aluminum has transformed modern industries. But while boats may not be among the most well-known applications for aluminum, the marine industry has undergone a technological revolution thanks to the unique properties of aluminum.

Whether we are talking about small personal watercraft or large shipping vessels, aluminum was almost certainly involved in the manufacturing process in some way. In some cases, the entire hull of a boat is made from aluminum, while in many vessels, particular parts and equipment are made from aluminum, such as ladders, railings, and gangplanks.

As has been found in many other industries, aluminum alloys offer a variety of characteristics that are ideal for marine applications, making it a better choice than competing materials such as steel or plastic. The question then becomes which alloy is best suited for the job at hand.

What are the major benefits of aluminum in the boating industry?

Aluminum has many desirable properties that have made it popular for boats and related marine parts. First of all, aluminum is lightweight, one of the most important considerations when designing a boat. But its lightness does not mean it isn’t strong. Aluminum alloys have been developed that can match or even surpass steel when it comes to strength to weight ratio.

Another point in favor of aluminum is its high yield strength, resulting in aluminum parts, in particular hulls, that can take quite a pounding before they begin to deform. Its combination of tremendous strength and extremely light weight is what has made aluminum so revolutionary in so many industries. In fact, for certain kinds of vessels, aluminum is too lightweight, and its use in the hull would make them too buoyant and susceptible to sharp dips and turns on choppy water. Of course, this is only an issue in a small number of cases.

To be sure, it is when dealing with marine environments, where salt water will be an issue, that aluminum truly begins to shine. Aluminum alloys are developed with corrosion resistance in mind. First off, aluminum’s natural oxidization process gives it tremendous protection from all kinds of elements. Plus, when potential corrosion is a primary concern, such as for boats and ships, protective coatings can be added, bolstering an alloy’s already high tolerance for salt water.

Furthermore, aluminum’s flexibility and formability mean that it is ideal for all sorts of marine applications. For example, even though aluminum will often be more expensive than steel, because working with aluminum is much easier, it ends up being a much cheaper manufacturing process. This includes that fact that aluminum is highly weldable, and can be worked with both as aluminum plate or extruded parts.

Which alloys are particularly well suited to marine applications?

One of aluminum’s great attractions is its tremendous diversity. There are numerous alloys to chose from, often with a spectacular array of refinements that offers manufacturers the ability to specialize for any given application. And while, because of the variety of parts and equipment that can be found on boats and ships, you are likely to find examples of every alloy series, two in particular are most popular.

First off, the 5XXX series of aluminum alloys are extremely popular on boats. These alloys offer weld yield strengths from 100 to 200 MPa and feature good weld ductility without the need for heat treatment. They are also renowned for their high corrosion resistance. Seawater tests have shown that after ten years of use, the tensile strength of 5XXX series alloys show reductions of only 2 to 5 percent.

Three alloys that are considered marine grade are 5052, 5083, and 5086. All three are produced primarily as rolled materials (in sheet or plates) and are commonly found in boat hulls. With high tensile strength at weld points and excellent corrosion resistance, these alloys are ideal for use in marine applications.

The 6XXX series offers two more alloys of marine grade that are particularly well suited to seawater, 6061 and 6063. The former, with a yield strength of 40,000 psi, is among the most commonly used aluminum alloys across all industries, and is again a top choice for boat hulls. The latter, while not as strong as 6061, does offer greater formability, and features a high surface finish that is good for anodizing.

What marine applications frequently use aluminum?

Boats with hulls made entirely of aluminum go all the way back to the 1890’s, when the first aluminum boat was built. As pointed out above, aluminum boat hulls are common for many types of today’s vessels, including fishing boats, pleasure boats, pontoon boats, and skiffs. But larger boats use aluminum hulls as well, and it’s a common material in fast ferries, which leverage aluminum’s lightweight to increase their top speed.

As an example, the Hawaii Superferry, with a length of 345 feet, is a fast catamaran with the ability to carry 1,000 passengers and 300 vehicles while traveling at 30-40 knots. The Benchijigua Express, one of the world’s largest aluminum hull boats at 413 feet long, is capable of going as fast as 36 knots with 1,350 passengers and 337 vehicles.

Of course, not all marine applications are boat hulls. No matter what material the hull is built from, many parts and pieces of equipment on board are likely to be made from aluminum, including windows, doors, ladders, railings, staircases, gangplanks, lights and light fixtures, pipes, tubes, outriggers, and more.

Summary

After over a century of use in the marine industry, aluminum alloys have proven themselves a durable, adaptable, and, most importantly, a corrosive resistant option for your boating needs. Clinton Aluminum adheres to a philosophy of “The Right Alloy for the Right Application” and we take pride in being a technical resource partner to our suppliers and customers. Call us today to learn more about how aluminum can help optimize your production process while saving you both time and money.

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