Understanding aluminum structural repairs

July 20, 2015
Aluminum and steel repair procedures greatly differ — are you doing them correctly?

If I were to tell you that repairing plastic bumper fascia is the same as repairing a steel panel, you would think I am crazy. So why is it there are so many people trying to convince people that repairing aluminum panels is the same as repairing steel panels?  In this third article of a six-part series, we will be discussing structural repairs on aluminum-intensive vehicles.  The OEM Certified Collision Facility programs started due to the differences in the repair processes for aluminum intensive vehicles and the lack of knowledge on how to repair them, and it all began with the European OEs and high-end vehicles. 

Mercedes-Benz 231 upper rail sectioning welded

Over the past 20 years as the European OEs have set the standard on the high-end vehicles, we have seen the influence of aluminum trickle down to the more popular vehicles.  Fifteen years ago many OEMs started to utilize aluminum for closure panels, bumper reinforcements and suspension components.  Then we saw the advent of hybrid construction (primarily steel monocoques with aluminum structural components) in the early 2000s, where strut towers are rivet-bonded to steel uni-rails, lower uni-rail (frame) extensions are bolted to steel uni-rails and multiple steel and aluminum monocoque structural components rivet-bonded to each other.  We have also seen the changes of anchoring the vehicles to the structural realignment apparatuses, where “pinch weld” clamping is prohibited and additional anchoring is required.

Structural repair overview

Anchoring
Celette, Car-O-Liner, CarBench, Global-Jig and Spanesi are very similar in design.  They are a machined top plane, rectangular steel structure where multiple fixtures (Celette) or universal jigs (the others) are affixed to the machined plane, which are then attached to the vehicle. The fixtures/jigs are utilized to measure the vehicle, except Car-O-Liner where they utilize electronic measuring with their EVO Jigs. Generally, there will be eight basic anchoring points at the front and rear suspension cradle mounting locations, with or without the engine or suspension cradles installed (the equipment allows for either anchoring depending on the extent of sustained damage and required repair procedure). On average, an additional two to eight anchoring points will be affixed to the vehicle, depending on the extent of damage. The additional anchoring point will also be utilized to install new OEM components to replace the damaged ones. A pull-back tower can be affixed to the apparatus, but in the case of most of the OEMs on aluminum-intensive vehicles, structural realignment is prohibited.

The Chief system is based on the American frame rack, which consists of a deck featuring tie-down openings for holding fixtures and two to three pulling towers. Chief offers a structural holding package that is compatible with other Chief and competitor frame racks in the market, while also offering a dedicated structural holding package for the aluminum-bodied Ford F-150. The vehicle can be measured while on the frame rack or on a two-post lift using Chief’s laser measuring system. Aluminum collet attachments are used to hold the measuring system’s targets in place on aluminum frames or bodies.

Structural repair procedures
What I am about to write may not make many happy, but it is the truth. Structural repair on aluminum-intensive vehicles are for the most part, limited to the following:

1.     Measure the vehicle on the approved equipment (no thinking or opinion here, you must follow what the OEM requires). After determining what components are misaligned, you will then know what must be changed. General rule of thumb is any direct and secondary damaged components will require require replacement. Ford is one of the very few OEMs that allows aluminum structural realignment; this is due to their extensive use of T4 aluminum, as opposed to the European and Tesla extensive use of T6 hardened aluminum. In the case of Ford, some secondary damage may be attempted to be realigned, but care must be taken to ensure no bonded areas are stressed. 

2.     After removal of the damaged components the mating areas will be prepared for new OEM component replacement, as per the OEM require procedures. Please keep in mind that some OEMs limit the sale of structural components to only its certified repair facilities.

3.     The new OEM components are then prepared, as per the OEM required procedures, and then affixed to the vehicle using the OEM required materials, protocols and equipment. The protocols may included any of or combination of rivets, rivet-bonding, bonding and/or welding. 

Now here is an issue you must be aware of when working with vehicles such as the Audi TT, Ford F-150, Mercedes-Benz S-Class, Porsche 911 or similar hybrid construction vehicles.  Because the vehicles are constructed from steel and aluminum, care must be taken during structural repairs not to cross contaminate the vehicle, equipment and clean room.

Porsche 970 lower uni-rail sectioning
Porsche 970 front lower uni-rail sectioning

For example, the 2015 S-Class V222 has an aluminum front and rear structural components attached to a primarily steel body (occupant area), the Ford F-150 is an aluminum upper body bolted to a steel perimeter frame and the Audi TT and Porsche 911 (991) are primarily aluminum monocoques with steel structural components attached. During the repair process, there may be times where you will be repairing aluminum and steel components due to the vehicle design and construction. For example, the Mercedes-Benz quarter panel is steel and is attached to an aluminum rear body panel and rear floor extension. When replacing the quarter panel, the steel portions are STRSW and the aluminum to steel areas are rivet-bonded with hardened steel rivets. During the drilling procedure, fragments of steel and aluminum particles can be tossed around the area, so you must insure that you use blankets and covers to protect any cross contamination. Blankets and covers will be required to cover the bench, undamaged areas and nearby equipment. Duct tape can be used to seal seams and crevices to prevent fragments from getting into those areas, which could cause galvanic corrosion over time. All the fragmented particles from drilling and sanding will need to be vacuumed up carefully. All blankets and covers will need to be vacuumed or washed.

Now the 2015 Ford F-150 has a little different issue. The upper body is all aluminum, except for the radiator core support and door intrusion beams, and the frame is steel. If you had an F-150 that had an impact to the right front corner, where the upper body and frame sustained damage, the vehicle will be repaired in the aluminum repair clean room. The repair procedures may include sectioning on the steel frame rail and sectioning on the upper aluminum rail. The same type procedures for cleanliness and protection would have to be adhered to. Remember — never use compressed air to clean areas for two reasons. The first is that the air will cause all the particles and fragments to become airborne, and those particles could wind up landing in areas that could cause galvanic corrosion. The second reason is most compressed air lines contain particles and oils, which would coat the aluminum and cause adhesion problems. 

Equipment
When getting prepared to get involved with aluminum repair, please keep in mind not all equipment is created equally and not applicable to other OEMs. There is a wide price range between some equipment. There are aluminum MIG welders out there for $3,500, $6,000, $9,000, and even $25,000. Comparable ranges can also be seen for some of the structural repair equipment and riveting guns. Many shops spend $75-$80k on one particular manufacturer, then they obtain another OEM certification just to find out that not all of that equipment is approved for the new OEM program, meaning they must purchase more equipment. Make sure you know what the requirements are for the OEM programs that work best for your business and think through the expenses and equipment decisions prior to opening your checkbook.      

Joining procedures        
In our next two articles, I will cover the different joining methods such as welding, riveting, bonding and/or any combination thereof.                            

We hope this third article, in a six-part series, has helped you understand some of the differences with structural repairs on Aluminum intensive vehicles. This is an overview, and we will delve deeper in to each area in detail in our following articles through 2015 and beyond. As always, if any questions arise please feel free to contact me.

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