Black coating on new panels

[fireguyfire]

I've decided to replace the entire quarter panel on the passenger rear of my 73 challenger; someone had done a bad job of hanging a quarter skin in the early 80's, and I've decided to go to the factory spot weld points and avoid having any longitudinal joint at all.
I've got an AMD quarter on the way, and I'm curious what you guys do with the black E coat that comes on these new panels to protect them; scuff it and prime over it? Or sand it off and start with bare metal for the new finish?

[cuda hunter]

https://www.e-bodies.org/videos/

Cody talks about what to do with the E coat.  Watch the videos. 

These are on the main page of this website. 

[captcolour]

I had a hard time finding the answer on the main page.  I did find this in the written articles and not the videos:

STEP 7 Metal Prep & Epoxy= Once you are completely done with all the metal work and trim fitment the next step is to prep any bare metal that was exposed during the metal work process.  If you replaced panels and they are in E-Coat, you do not have to scuff them.  The DP epoxy with 401 hardener will stick right to the E-coat.  E-coat was not meant or designed to be scuffed.  I personally prefer to remove all the E-Coat with 150 sand paper on a DA then do my metal prep over bare metal.  Also scuff all of the old epoxy on the exterior panels with a red scotch bright or 320 sand paper.  Completely prime the exterior of the vehicle with 1 to 2 coats of DP epoxy giving it a solid even coat of protection for the body work to be done on top of.  Wait 24 hours before starting step 8 body work.

[torredcuda]

I also prefer to sand it all off as I don`t trust anyone elses prep work including the factory making those panels.

[RUNCHARGER]

Exactly: There is no assurance that the sheetmetal was perfectly clean with absolutely no surface rust or oil on it before it was e-coated.

[JS29]

The factory panels have instructions that tell the procedure Is to not remove the E-coat. it will void any rust warranty. AMD panels in my opinion have high quality E-coat on them.some of the after market parts, not so good. I can usually tall when i am sanding them, how well it is adhered to the part.   

[76orangewagon]

I asked the same question once to a professional painter who was painting my Duster and here was his answer "Do you want to trust a $10,000 + paint job to underage and underpaid Taiwan boy who applied that coating". It might not be politically correct or 100% accurate but the message was 100% clear. I stripped the E-coat off every panel. 

[7E-Bodies]

As mentioned above, I've gone with Cody's suggestions to the exact detail. I'm using all PPG materials he lists. I sand off the entire exterior of the new panel as he mentions and treat it with the metal prep exactly as he describes. Results are phenomenal. The insides I scuff with the red ScotchBrite pad he recommends and spray 3M undercoat everywhere except where I've sprayed RestoRick's factory appearance undercoat (except for the areas that are to be welded, I use 3M Weld Thru primer from a rattle can). See "How to Paint a Show Car Finish" at https://www.e-bodies.org/videos/

[GoodysGotaCuda]

E-coating process is pretty robust when done well, it's a gamble on if it's best to remove it or not.

IF the e-coat is done properly, you'd be far better of leaving it on. It's a great corrosion barrier.


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[jimynick]

  Yep, that's my opinion too, and I never apply ANY paint product onto an unsanded surface, period. Chemical adherence is nice, but mechanical adherence in addition to said chemical is better IMHO. Read the info charts for your materials. it should give factory recommendations as to how to use it. 

[7E-Bodies]

I have yet to find a panel rotting from the outside in. That being said, I sand the black to bare steel on the outside of the panel only. I then treat it with PPG recommended products and epoxy. The inner areas get red scotch brite scuffed and 3M paintable undercoating.

[fireguyfire]

What grit do you guys use to prep bare metal for primer? Seems to be some debate out there between 80 grit, and 150

[JS29]

I like to give it something to bite into, 80 grit.  Than give it an extra coat.