Over the last two decades, aluminum materials have become a viable option for several vehicle makers. Aluminium panels and structures are lightweight, resistant to corrosion and recyclable. Being able to asses damage to aluinum panels and structures requires understanding its properties, characteristics, design, and construction. This knowledge can help direct repair vs. replace descision and support a safe and complete repair.
Do’s and Don’t of Aluminum Repair –
Vehicles that use aluminum are grouped into two categories.
The first group includes vehicles built with varying aluminum parts. The second group includes aluminum-intensive vehicles that use larger amounts of aluminum in parts such as strut towers, pillars, drive train mounts, engine cradles, rails and rocker panels. (Vehicles including the Audi A8, Acura NSX, Honda Insight, 03 Jaguar XJ and the Mercedes-Benz CL Class) use aluminum as a structural component. They use aluminum exterior panels attached with mechanical fasteners, bonding, weld bonding, bonding with mechanical fasteners, clinching and squeeze-type resistance welding.
Aluminum-intensive vehicles use sheet (the most widely used), extruded and cast aluminum.
The use of aluminum parts on highly produced vehicles such as the F150 and some General Motors vehicles has been restricted to outer parts that can be removed and replaced. When damaged, these parts have largely been replaced instead of repaired however, repair attempts using traditional steel methods and tools have met with unforeseen failure.
Do not repair outer aluminum parts. (Replace outer aluminum parts)
As the use of aluminum in the manufacturing of vehicles has increases and we now find aluminum used as structural parts, technicians must learn new repair processes for them as well. Different types of aluminum are sensitive to heat. The way that aluminum responds to the pulling forces is also somewhat different than steel, and different tests and precautions must be used when repairing it.
Alloyed aluminum is grouped into two categories: heat-treatable and non-heat-treatable.
The heat-treatable group includes: 2000 series (alloyed with copper) used often for body panels; 6000 series (alloyed with magnesium), also used for body panels; and 7000 series (alloyed with both zinc and magnesium, making it very strong), used for applications such as bumper reinforcements.
Non-heat-treatable aluminum includes: 1000 series (nearly 99 percent pure), which is very soft and used for electrical wiring; 3000 series (alloyed with magnesium), used for interior structures; 4000 series (alloyed with silicon), often used for electrode welding wire; and 5000 series (alloyed with magnesium), often used for inner structural parts.
Aluminums soften when heated, thus allowing technicians to repair collision-deformed aluminum more easily. Both heat-treatable and non-heat-treatable aluminum alloys may be heated to repair, but as with steel, these alloys may also be damaged with heat if the recommended temperature is exceeded.
Unlike steel, aluminum does not change color as it heats, thus making it nearly impossible to judge temperature by eye as the material is heated. Aluminum also has a critical temperature at which it "anneals" or permanently softens. This temperature is below its melting temperature, but above its repair threshold.
Do not exceed recommended temperature to soften heat-treatable and non-heat-treatable aluminum alloys.
Technicians must be very diligent when using heat to repair aluminum to stay within the repair temperature limits.
Do carefully monitor the temperature of the aluminum
Heating aluminum can be monitored using heat detection crayons, heat detection paint, heat monitoring strips, non-contact thermometers or thermocouples found as probes on a digital volt meter. Because of the high temperatures needed to reach the relatively low threshold (400-570 degrees F), careful monitoring should be observed.
Do carefully detect the cracks
Cracks may be very small and difficult to detect, so repair technicians must use a dye penetrate to detect small cracks.
Do not - repair cracks in aluminum structural parts (Do replace the structural part)
Or risk driving with unsafe parts which can cause injury when involved in an accident.
Do - make certain technicians are specifically trained to aluminum repair and are certified aluminum welders so they are able to test and inspect the repairs that they complete to assure their repair quality, and also in order to be aware of and be able to eliminate galvanic corrosion.
Technicians should be full trained on the basic physical properties of aluminum as well as be able to:
- Explain aluminum properties and characteristics and be able to identify their differences.
- Be able to identify vehicle part design
- Analyze damage to aluminum exterior panels and identify repair procedures
- Analyze damage to aluminum structural parts and understand repair considerations
- Understand the considerations around making repair vs replace decisions
- Identify different areas of repair facility and understand the functions of specific equipment