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Corrosion Resistance of Aluminum Alloy Families


Corrosion resistance is one of the foremost benefits of aluminum, as evidenced by its tremendous popularity among manufacturers and product designers.   It’s important to recognize that each family of aluminum alloys offers varying degrees of corrosion protection.

Aluminum, despite only becoming commercially viable as a material in the last 100 years, is well known for its strength, light weight, durability and sustainability.  This has led to an explosion in the use of aluminum across nearly every industry, including automotive, food handling, aerospace, architecture, consumer electronics and more.

How are aluminum alloys categorized into families?

An aluminum alloy is a chemistry specific grade of aluminum that has had its composition altered by the addition of other elements.  This is done to enhance certain properties in the aluminum while retaining others.  Though alloying is a process used with most metals, it is especially necessary with aluminum because pure aluminum has very low mechanical properties and is extremely reactive with other elements.

The elements typically added to pure aluminum include iron, silicon, copper, magnesium, manganese, molybdenum and zinc. The amount of each alloying element determines a grade’s characteristics; all together the alloyed elements can make up as high as 15 percent of the material composition.

The system for categorizing various aluminum alloys is overseen by the Aluminum Association.  It administers the allocation and registration of new alloys, which  presently number over 600.  Anyone interested in a better understanding of the alloy designation system should reference the publication, “International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys.”

Aluminum alloys are divided into families based on the primary alloying element utilizing a 4-digit system.  The first number of the designation, such as 6 in 6061, indicates which family that alloy belongs to.

1XXX series

Grades belonging to this family of alloys, such as 1100 & 1350, are composed of primarily pure aluminum.  1100 is 99% aluminum while 1350 is 99.5%.  As such, these grades have very high corrosion resistance and electrical conductivity.  This is balanced by their relative lack of strength and hardness, and they are often used in enclosures, bus conductors and other applications where ductility and conductivity are valuable properties.

2XXX series

This family of heat-treatable alloys uses copper as its primary alloying element.  This makes these alloys both strong and tough across a wide range of temperatures, thus a popular choice of the aerospace industry.  However, these alloys are known to be susceptible to atmospheric corrosion, and thus it is often necessary to further protect 2XXX series parts with an added coating.  2024 is a popular grade in this category.

3XXX series

Manganese is the primary alloying agent in the 3XXX series of alloys.  This family is known for having decent strength and good formability, while still being suitable for anodizing and welding.  In terms of corrosion resistance, they perform well, making them popular in a variety of industries.  These alloys can be found in pots and pans, cooking utensils, automotive trim, heat exchangers, chemical handling components, and beverage cans.  3003 is the most widely used grade of aluminum in all industries and markets.

5XXX series

The 5XXX series of aluminum uses magnesium as the primary alloying agent.  While not heat-treatable, these alloys are very popular thanks to their excellent strength, weldability and ductility.  They are also famous for offering good corrosion resistance, even in marine environments.  This combination of strength, weldability, and corrosion resistance means these alloys can be found in shipbuilding, transportation, building and construction, including bridges, storage tanks, pressure vessels, as well as a range of marine applications.

6XXX series

Both silicon and magnesium are the main alloying agents of the 6XXX series of aluminum. These heat-treatable alloys are prized for their versatility, strength, and durability.  They offer a balance between the high strength of the 7XXX series and the corrosion resistance of the 5XXX series, having comparably moderate corrosion resistance.  It’s no surprise then that these alloys can be found in so many different industries.  6061 is one of the most specified grades on the market.

7XXX series

For the 7XXX series, the main alloying agent is zinc.  They are both heat-treatable and extremely strong.  Among the grades we are discussing today, the alloys in this family have the lowest corrosion resistance.  The primary uses for these high-strength, lightweight alloys are in aerospace applications.  7075 and 7050 are both commonly specified grades for the aerospace industry.

Your Technical Services Provider

One of the most important jobs of a manufacturer is picking the right material for each application, which requires balancing a variety of factors, including performance, sustainability and cost.  For any application that will be exposed to the elements or requiring a long lifespan, adequate corrosion resistance is essential. That’s why so many companies choose to work with Clinton Aluminum.

As the Midwest’s number one aluminum supplier, Clinton Aluminum is committed to working with our clients through every step of their procurement process.  If you’re looking for corrosion resistant aluminum alloys, contact one of our experienced and knowledgeable customer service representatives today.

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