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Working with aluminum

Friday, July 25, 2014 - 06:00

Aluminum is the most abundant metal and third most abundant element in the earth’s crust. Vehicle manufacturers are producing more models with this beneficial metal everyday. Demand for aluminum repair has increased rapidly in recent years and will continue to do so. Already 30% of all the hoods and over 20% of the bumper beams are aluminum. Body, bumper & closure parts account for 58% of the aluminum content growth from 2009 to 2012. Shops eager to capitalize on this market need to do two things: learn how to work with aluminum and re-tool with tools specific to this type of repair.

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It is best to eliminate excessive arc by lower the power setting just enough so the pin welds with minimal spark to no spark.

Reasons for Usage
More than ever automotive manufactures are using lightweight materials to improve fuel economy and turning to aluminum to create these lighter components. Lighter can result in better mileage, smaller engines moving less mass and greater acceleration. US Governmental initiatives has accelerated the weight loss of production vehicles by mandating the Corporate Average Fuel Economy (CAFE) standards of 54.5 mpg by 2025. Companies realize it makes economic sense to utilize this abundant, recyclable resource that makes up about 8% of the earth’s crust. The top selling pickup in history, the Ford F-150, has been redesign and will feature aluminum in its build materials in 2015. 

Things to Know
Aluminum behaves differently than steel.
Change the shape of a steel part; it remembers the form it used to be in. The opposite is true when working with aluminum. Once it is reshaped it forgets its original form and will take on a new shape.

It is a work hardened material. When aluminum is stamped into shape it becomes stronger. After the panel is bent in a collision it becomes stronger still. Flex it too much and it breaks or cracks like a bent spoon. In order to repair and pull the damaged area, the panel must be heated to 350°F to allow the metal to soften. Aluminum dissipates heat very quickly but can become permanently changed if heated past a certain point, approximately 450°F. The heated panel can now be pulled and while pulling the material it is being work hardened to set the new memory.

A thin coating of aluminum oxide forms after being exposed to the air in as little as 15 minutes. This oxidation has a much higher melting temperature than the original aluminum material and a stud will not fuse correctly to the panel. Aluminum’s melting point is 1,200°F and aluminum oxide is 3,600°F. The oxide can be removed using a stainless steel brush.

Galvanic corrosion will occur when a less “noble” metal like aluminum, comes in contact with a more “noble” metal like steel, in the presence of an electrolyte suck as water. The aluminum will corrode around the steel contamination, ruining the finish paint. In order to avoid contamination a separate set of working tools and separated work area must be maintained. Steel bolts, screws or rivets should not be used when in direct contact with aluminum unless properly coated.

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Identification
A quick method is to use a magnet, it will not be attracted to an aluminum panel. There are alloys and different manufacturing methods that determine the series of aluminum. It is a good idea to refer to the manufacturer literature for series identification of cast and panel pieces. In all cases manufacturer methods and guidelines on whether to repair or replace should be always followed. However, not all companies make this information available. Another great resource to utilize is the internet. A basic search for high aluminum content brought me to the free information provided by the Aluminum Association (www.autoaluminum.org). The site contains loads of information about the aluminum industry and a database of vehicles with high aluminum components. Once it is determined that the damaged part is made of aluminum, the next step is to understand what the 4 digit series means.

Aluminum alloys are designated into 4 digit series based upon the main element used in combination of the aluminum. The most common use for automotive applications are 5000 and 6000 series which mostly contain Magnesium and Silicon. Any number that follows the first digit identifies the percentage of alloying agent used. These alloys are further classified as Heat-Treated and Non-Heat-Treated. This means that during the manufacturing process they have the ability to gain strength from being exposed to elevated temperatures or from being stamped or bent. Click the chart below to enlarge.

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