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Corrosion Repair on Aluminum Body Panels
The days of rusting steel body panels are over. With the introduction of galvanized-coated steel and advanced corrosion coatings, rusted rocker panels, fenders, floor pans and door seams are history. As a result, overall vehicle life has increased, as well as the value of used cars, minivans and light trucks. In addition, alternative materials that do not rust have made inroads into the makeup of the modern vehicle. One of these is aluminum.
Aluminum is a wonderful metal. It is strong, it can be easily formed using the same methods as steel, and it is about one-third the weight of steel. In other words, automotive parts can be made thicker and stronger while still reducing weight. It is soft, non-magnetic and ductile and can be painted to a grade A finish. Aluminum is the most abundant metallic element in the Earth’s crust, so there will not be a shortage of it anytime soon. Due to its light weight compared to steel, aluminum has replaced steel in those applications in which weight savings is more important than strength.
Aluminum is now commonly used for hoods throughout the FCA US LLC vehicle lineup. Also, you’ll see it used for door sheet metal, fenders, hinges, swing gates and liftgate panels. Next time you lift a hood on a minivan, notice how light it is. That is due to the use of aluminum.
Another benefit of using aluminum instead of steel is the fact that aluminum does not rust and will not corrode in the same manner as steel. If unprotected, steel will rust and that rust will continue to consume the rest of the non-rusted metal. Aluminum surfaces will corrode, but once the entire surface has a thin layer of corrosion, the corrosion stops. Aluminum will not consume itself in the same manner that steel does when it rusts. Unfortunately, minor aluminum corrosion issues have appeared on some FCA US vehicles. These issues are cosmetic, not structural, in nature. The problem is not widespread and repairing the surface imperfections is rather straightforward. The problem first appeared on some 2013 models (Challenger / Charger / 300 / Ram 1500 / Minivans) and other more recent models. to eliminate that corrosion and return your customer’s vehicle to “as new” condition.
A Collision Bulletin was prepared to deal with this problem, detailing the procedures to correct these corrosion problems. Released several years ago, the current version is 31-002-20, dated October 27, 2020. In this Body Repair article, we will review this corrosion issue and detail the steps required.
Visually, this condition will appear as corrosion, or bubbling, on the leading edge of a hood, or other exterior aluminum surfaces. To determine if a panel is aluminum, refer to the collision manual for material specifications. If the panel is a hood, it probably is aluminum. A good example of what this corrosion looks like can be seen in Figure 1, the leading edge of an aluminum hood.
In many cases, this corrosion can be removed and the panel can be repaired. Let’s review this repair procedure with our example being the leading edge of a hood on a mid-2010’s minivan.
Remove the hood from the vehicle in the following manner:
From the underside of the hood, remove the push-in retainers that secure the rear edge of the hood silencer pad to the inner hood reinforcement. Disconnect the washer plumbing fitting from the barbed nipple of the washer nozzle.
Refer to Figure 2. Using a grease pencil, mark the location of the hood hinges ③ on the hood ② to aid re-installation. Remove the nuts ① attaching the hinges ③ to the hood ②. With the aid of a helper, remove the hood ② from the vehicle.
Caution: For any panel with exterior mounted hinges, avoid removal of the hinge from the Class A panel unless absolutely required; this will minimize the risk of breaking paint around the hinge perimeter which can create further damage.
Remove all trim components necessary to repair the damaged panel. Wash the panel with soap and water to remove all dirt and debris. Grind the corroded areas of the affected panel to bare aluminum using a right angle grinder equipped with an 80 grit grinding disc. After removing the corrosion, feather sand the area of the panel with 180 grit sandpaper. Finish sand with a 3M® Scotch-Brite Scuffing Disc 07467 Maroon, or equivalent.
Sand the remaining exterior painted surface of the hood with 800 grit sandpaper. Prepare the hood for refinishing. Remove all the remaining dust by cleaning the hood with PPG® DX330 Wax and Grease Remover or equivalent. Tack cloth the surface.
Note: PPG is referenced as the primary product, but other refinish paint manufacturer brands are acceptable; refer to the list in the collision bulletin.
Apply Mopar® 06103087AA Anti-Corrosion pen to the repaired areas (see Figure 3). Remove the red cap to expose the felt pen applicator. Brush the felt applicator across the repaired areas. Next, apply PPG® DPLF primer epoxy primer to the bare aluminum only.
Note: Do not apply corrosion protection material on SMC (plastic) panels; the paint and other coatings can be adversely affected; in some instances, it can cause a condition referred to as solvent popping.
Apply PPG K36 primer surface over the repair area only. When the surface primer has cured, block sand the surface area with 500 grit sandpaper to prepare it for primer sealer application. Prepare the hood for refinishing. Remove all remaining dust with PPG DX330 Wax and Grease Remover, or equivalent. Tack cloth the surface.
Apply primer sealer and allow it to flash. Next, apply 2-3 coats of basecoat and allow it to flash. Then, apply 2-3 coats of clearcoat and allow it to cure.
To finish the repair, re-install the hood. Tighten the retaining nuts to 18 ft-lbs. Install the removed trim components and replace any adhesive backed components (e.g., nameplates). Also, re-connect the washer plumbing fitting to the barbed nipple of the washer nozzle.