What to know as you prepare for aluminum

Aug. 20, 2015
Analyzing and repairing damage to aluminum vehicle components is no more difficult than for traditional steel vehicle components. All you need is the right equipment and a basic understanding of how aluminum characteristics affect the repair process.

If you are feeling a bit lost in all the new aluminum-specific information being shared by OEMs, trainers and industry experts, you’re not alone. Since steel has been the go-to metal for vehicle bodies for the past century, there’s been little need to learn about aluminum characteristics and repair procedures unless you worked on specific high-end vehicles. Steel has 100 years’ worth of repair development behind it, while many repair professionals are just starting to learn more in‑depth information for aluminum repairs.

Aluminum damage analysis should always include the measurement of the entire vehicle. Today’s vehicles are designed to transfer collision forces around the passenger compartment, and measuring provides the only assurance that no “hidden” damage will be missed.

New MIG/MAG welders designed specifically for aluminum’s high thermal conductivity can make welding aluminum as easy as welding steel.

Fortunately, analyzing and repairing damage to aluminum vehicle components is no more difficult than analyzing and repairing damage to traditional steel vehicle components. It is just different. All you need is the right equipment and a basic understanding of how aluminum’s characteristics affect the repair process.

Understanding and analyzing aluminum
Automakers are swapping aluminum for steel in body components because aluminum helps them save weight without sacrificing strength. An all-aluminum “body in white” vehicle structure can weigh as much as 50 percent less than a traditional mild steel body, which helps improve fuel efficiency.

When designing a car or truck, OEMs have an array of different aluminum alloys and manufacturing options to choose from. When analyzing aluminum damage, it is important to use the OEM’s repair guidelines to determine which types, if any, of repairs are allowed. In general, damaged aluminum parts that are cast should be replaced. Some damaged extrusions may offer limited repairability; and stamped aluminum parts  may be repairable depending on the extent of damage and vehicle manufacturer recommendations.

Regardless of what materials are used in its manufacture, the only way to ensure all collision damage is found during the vehicle analysis process is to measure the entire vehicle upfront. Standard collision dynamics, which show how the forces involved in a collision travel beyond the point of impact, apply to cars and trucks built with steel and aluminum. Because aluminum may be susceptible to micro‑cracking, estimators should be sure to inspect for cracks. Dye penetrant is available for areas where cracks are suspected, but cannot be seen with the naked eye. Because adhesives, in conjunction with rivets, are also used for many aluminum vehicles, potential failed bond areas should be closely inspected. Once all body damage has been assessed and the vehicle structure has been measured, the estimator and technician can develop a comprehensive repair plan.

Aluminum preparation
Before you get started working on aluminum vehicle components, there are several things to keep in mind:

Galvanic corrosion can be a concern. The hammers, dollies, and other equipment that you use to repair steel should be cleaned before use on aluminum. That’s because residual steel particles left behind from a previous repair could potentially cause galvanic corrosion on the aluminum part being repaired.

Many OEMs require aluminum repair areas to be isolated from the rest of the shop with either curtains or walls. A dust extraction system should also be used to collect the hard-to-contain airborne particles created during sanding. Be sure the dust extraction system is designed for aluminum use.

Once you have the right tools and training, and your shop is sufficiently configured to contain the repair, you can start repairing aluminum vehicles.

Since steel corrodes aluminum, the process for removing dents from aluminum panels requires dedicated tools. Any pulling bars and hammers used should be made of aluminum, and they should be kept separate from tools used to work on steel. 

The pulling bar method for removing dents from aluminum panels requires a stud welder specifically designed for aluminum. These welders deliver very brief but high current density to break through surface oxidation and insulation without damaging the metal. 

Removing dents
When aluminum deforms during a collision, it is work‑hardened. This can make removing damage difficult. With the right tools, though, it is possible to remove dents from exterior aluminum body panels.

There are multiple methods for removing dents from aluminum panels: conventional hammer and dolly techniques, weld‑on dent removal tools, adhesive dent removal tools, PDR, and with heat.

Weldon and adhesive dent removal equipment
While you are likely well-versed in conventional hammer and dolly techniques, along with steel weld‑on dent pulling equipment, you may not be as familiar with some of the tools that have been developed for aluminum. These aluminum-specific dent removal kits come with conventional pulling attachments and special hammers. You’ll also need a stud welder designed for aluminum, as well as aluminum studs.

Heat
Although challenging, heat alone can be used to remove some, minor, dents. Because aluminum conducts heat away from its source very quickly, proper repair techniques are required to localize the heat and create the internal stress needed to force the panel back into shape.

Aluminum also melts at a temperature that is less than half that of steel, and does not change color once it reaches its melting point. For these reasons, aluminum heat shrinking requires careful attention to temperature and the heat effect zone. Excessive heat will also anneal the panel, this will permanently soften the panel. The technician should closely monitor the work area with a heat monitoring device. .

Aluminum joining
MIG welding and rivet‑bonding are the main methods for joining aluminum during collision repair. OEM repair procedures provide guidance on when and where to use each joining method.

MIG welding
Aluminum MIG welding requires new training, different techniques and transfer methods, vehicle maker recommended electrode wire, and 100% argon shielding gas. Aluminum welding is susceptible to cratering – when not enough filler is added to the weld – and cracking. Aluminum’s high thermal conductivity can also lead to incomplete fusion, particularly at the start of the weld when there is not enough retained heat in the material.

New MIG welders have been developed to help solve these issues. Some machines offer crater fill capabilities, hot start features, and preset aluminum welding programs. Some models come with push-pull feeders, which help keep uniform tension on soft aluminum wire.

The use of riveting to join aluminum to steel is growing as automakers continue to mix the two metals in vehicle bodies. Advanced self-piercing rivet guns streamline the repair process by eliminating the need to drill a hole for each rivet. 

Riveting
Rivets are ideal for joining aluminum as well as steel. As automakers increasingly mix metals in new vehicle construction, the use of rivets will only increase.

To start riveting, you will need a rivet gun and the appropriate rivets for the repair. Solid rivets require a hole to be drilled in the material, with enough space on both sides of the joint to press the rivet against a backing anvil. Blind, or “pop,” rivets require access on only one side, so they can be used in hard-to-reach areas. Self-piercing rivets require a self‑piercing rivet gun and rivet‑size specific dies and mandrels. With self-piercing rivets, there are no pre‑drilled holes required; the rivet pierces the aluminum.

The specific rivet(s) required for each part replacement procedure will be based on the vehicle maker procedure. It’s important to use the rivet requirements found in the body repair manual.

Understanding aluminum’s unique characteristics can help you prepare your shop for the future. For more in-depth information, be sure to enroll in one of the many aluminum-specific collision repair training courses held across the country this year.

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