At the folded seam for inner and outer doors is the applied order... EDP coating, epoxy primer, seam sealer and paint? or EDP coating, seam sealer, epoxy primer and paint?
I have applied 3M seam sealer over epoxy primer and electo deposit coatings, and under epoxy primer, but never under EDP so I can't help there. I would think that EDP is like powder coat and may not adhere to the seam sealer. But I do not have experience to back that up.
I have an earned distrust for EDP. Three times now I have wiped it with acetone, only to have it come right off, indicating that it was just cheap black paint.
What is the process for Electrocoating? EDP Electro deposition primer (E-coat) In the first step – pretreatment – metal is cleaned and a phosphate is applied to prepare the surface for application of the e-coat. This process is essential to achieving the performance requirements desired by product end users. PPG Coatings Services analyzes the metals to be processed and chooses the most appropriate chemicals for cleaning and phosphating. In our facilities, the most common pretreatment regimen for steel and iron parts is immersion in a high-quality zinc-phosphate system. During the next step, coatings are applied to the pretreated metal in an electrocoat bath using precisely calibrated process control equipment. The e-coat bath consists of 80-90% deionized water and 10-20% paint solids. The deionized water acts as a carrier for the paint solids, which are under constant agitation. The solids consist of resin – the backbone of the final paint film, which provides corrosion protection, durability and toughness – and pigments, which contribute color and gloss. Post-rinsing, which occurs next, enhances the quality of the coating and enables the recovery of excess paint. During the e-coat process, paint is applied to a part using a regulated amount of voltage to achieve the desired film thickness. Once the coating reaches the prescribed thickness, the part “insulates” and the coating process slows down. As the part exits the bath, paint solids that cling to the surface are rinsed off to maintain application efficiency and aesthetics. This residue material, which is called “drag out” or “cream coat,” is returned to the tank, enabling the e-coat process to achieve application efficiency rates above 95%. After the coated part exits the post-rinse phase, it is placed in a bake oven that cures and cross-links the paint film to maximize its performance properties. The minimum bake time is 20 minutes with a part temperature at 375°F for most e-coat technologies. PPG Coatings Services can also apply a supplemental “low temperature cure” e-coat material depended on volume. Most, if not all, OEM automotive manufacturers use this process, or similar, for replacement parts--aftermarket parts manufacturers, probably not. I emailed (about 4 years ago)a large aftermarket importer of automotive replacement parts and asked if the primer was an actual electro deposition primer and if the steel was phosphated before the process. Surprisingly, about a week later I did get an answer, that the steel was cold rolled steel with no phosphate coating and the primer was just a "transport" primer coating. If you have noticed pits or rusting under the primer on aftermarket parts, those parts were probably exposed to humid conditions before priming and shipping and never had a phosphate coating. As for me, I will strip the primer/coating and probably metal etch or at least etch prime the panel before proceeding with my primer/paint system. If there is rust under the primer it is NOT "E" coat, just a transport primer. The first part of the EDP process is phosphate coating of the bare steel. In the first step – pretreatment – metal is cleaned and a phosphate is applied to prepare the surface for application of the e-coat. This process is essential to achieving the performance requirements desired by product end users. PPG Coatings Services analyzes the metals to be processed and chooses the most appropriate chemicals for cleaning and phosphating. In our facilities, the most common pretreatment regimen for steel and iron parts is immersion in a high-quality zinc-phosphate system.
Ive tried some of this stuff... on small patched/rust cleaned areas for temporary seal https://www.spraymax.com/en-us/products/product/primer-primer-filler/1k-e-coat-primer/ ,
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