There are certain rule of thumb conditions when repairing any type of corrosion:
All rust / corrosion must be removed or it will return.
Sand blasting / grinding will remove surface rust but it won’t remove rust from deep in the pitting.
Any bare metal around the repair must have a corrosion resistant material applied to protect against future corrosion
Note: Most corrosion removing / neutralizing chemicals have safety / health concerns. Always follow manufacturer’s recommendations when using corrosion removal equipment and chemicals.
Corrosion Perforation Overview:
Corrosion perforation is any hole that has formed because of a corrosion condition. When repairing corrosion perforation you must remove all corrosion prior to beginning the repair.
A cosmetic body panel does not require replacement in all cases of perforation. A new partial panel can be hand crafted or cut from an OE panel to accomplish a good lasting repair.
Corrosion perforation can be repaired using a repair panel and the overlap process or the backer panel process. The type of section to be used is usually determined by the location of the condition. A lower quarter panel can usually be repaired using the overlap procedure. On the other hand, using a backer panel to repair corrosion on the roof would be a better choice. Areas like a roof, which require a smoother transition of the new replacement panel and the existing panel, the backer process usually works better.
Roof Panel Repair Overview:
When evaluating a corrosion condition on a roof panel you need to take into consideration things like extent of the condition. Will you need to remove the windshield to do the repair? Can a repair be made without removing the headliner? What type of joint would be best suited for this particular repair?
Roof Panel Repair using a Backer Panel:
Remove all parts necessary to access the damaged area.
Remove all the corrosion from the panel being repaired. If there is any corrosion left behind, even if it’s deep in the pitted areas the corrosion will return.
All paint, primer, adhesive, and any other protective coatings must be removed from all mating surfaces prior to application of any adhesive for the backer panels. Grind a 2.5cm (1 inch) contact area on all panels where you will do your backer panel bond. The metal should be bare and shiny in appearance. The panels to be used as the backer panels must also be free of all coatings. Bevel the backer panel to prevent moisture or condensation from collecting between the panels.
Pre-fit the backer panels to the roof and the insert patch to ensure a proper fit. If screws will be required to hold the backer panels and the insert in place during application they should be used during the dry fit.
Using Mopar (part # 05083855AA)/ Fusor #112B dispense a small amount of adhesive with out the tip to assure there is an even flow of adhesive from booth sides of the cartridge. Once you are sure there is even flow, install the mixing tip and pump the adhesive through the mixing tip.
Note: Apply the structural adhesive to all bare metal at the bond area. The adhesive has corrosion resistant properties built-in to protect the metal from corrosion.
Apply 3/8 to 1/2 inch of Mopar / Fusor #112B to the mounting area of the insert panels. From this point you will have approximately 70 minutes @ 21°C (70°F) to apply the adhesive and assemble the components.
Use a body filler applicator to smooth the adhesive and to cover all bare metal to prevent corrosion.
Position the backer panels into place using the clamps and/or screws from the prior dry fit process.
You may need to smooth or finesse the adhesive at the bond surface prior to installing the insert/repair panel.
Apply a small amount of adhesive to the underside of the insert/repair panel at the bare metal spots to ensure there will be corrosion protection
Secure the insert/repair panel in place using clamps and/or screws from the dry fit process.
Remove all excess adhesive material from the work area.
Once the adhesive has achieved handling strength in approximately 2 ½ hours, remove the clamps and/or screws.
When the adhesive has reached full cure, if screws were used bevel the screw-holes and prepare the joint and screw holes for the application of waterproof fiber-filled body filler. Complete the repair using conventional body filler.
Refinish following paint manufacturer’s recommendations.
Hem Flange Corrosion Overview:
Hem flange corrosion generally starts at the bottom of a down standing hem flange where water can collect. The condition can occur on hoods, liftgates, and door skins. The condition usually begins where the outer panel makes the turn upward to form the hem flange on the inside of the panel. The condition can vary from minor surface corrosion to perforation. The repair process will vary based on the severity of the condition.
Hem Flange Repair:
When the condition is surface rust at the edge of the hem you would remove the corrosion, and apply a corrosion resistant primer. Seal the hem edge using seam sealer and topcoat following paint suppliers recommendations.
A slightly more aggressive corrosion condition may require opening of the hem to remove all the corrosion. Once the hem is opened you must remove all the corrosion and apply a corrosion resistant material to protect the sheet metal.
A couple of the most common corrosion resistant primers are acid etch primers and epoxy primers.
The adhesive The Chrysler Group recommends for hem repairs contains corrosion resistant properties (built in) so no primer is required.
Once the corrosion is removed from the hem area apply the Mopar / Fusor #112B adhesive, follow the directions that are supplied with the adhesive.
Move the hem back into place remove any excessive adhesive squeeze-out. After the adhesive has cured finish sand, prime, seam seal and paint.
Hem Flange Removal Repair:
In cases where there are parts of the hem missing or the hem is very thin it may be easier to remove the hem completely to achieve an acceptable repair.
The outer door skin is bonded to the inner door structure around the perimeter of the door assembly. The hem is applied during the assembly process to hold the inner and outer door panels together until the adhesive is cured using heat from the paint process. Once the adhesive is cured there is no need for a full hem flange.
Use a grinder equipped with a 36 grit-grinding disc to remove the hem flange by grinding through the lower edge of the door skin. To do this you must use the grinder so the rotation of the grinding disc moves inward toward the inside of the vehicle at the cutting surface. If the grinding disc moves outward away from the door skin on the cutting edge you will peel the outer door skin away from the inner door causing damage to the skin.
Once you have cut through the skin, peel the remaining hem from the inner door.
Check the bond between the inner and outer door panels, at the bottom of the door if there are locations that require adhesive bonding use Mopar (part # 05083855AA)/ Fusor #112B structural adhesive. Follow the information on the instruction sheet for curing and work time.
Note: There must be drain holes in the bottom of the door. If you apply adhesive to the bottom of the door make sure to you have a drain hole at the front and rear of the door.
Finish sand, prime, and topcoat per paint supplier’s recommendation.