Remove black protective coating off new MB panels or not??

[Scottcorvette]

I have a new rocker assembly from Mercedes, it has the black protective coating on it which I was planning on removing and then priming with the same primer as the rest of the car. What is the general consensus on this? wasting my time or a worthwhile exercise?

All the other panels I have bought have been either bare steel, had some grey mottled paint on, or the MB black but have been pretty scratched up so I have stripped it off but this looks in nice shape, wondering whether I ought to just key it up and prime over the top.

I stripped the black off the new rear panel and there was a little bit of brown on the metal underneath the coating in places but in fairness that could have been as a result of the paint stripper, it was scrubbed with scotchbrite/thinners and was fine.

My Mustang doors had the same stuff on them and I think the painter just scuffed them up, the paint hasn't fell off them yet....

[Benz Dr.]

I would remove it on body panels. The rocker is heavy gauge material and is more prone to rusting from the inside so it's not as big of a factor.

One thing I see a lot of is where body shops leave the sticky part number labels on the inside of replacement panels. This will cause rusting over time as the label absorbs moisture. Always remove those sticky labels!

[Shvegel]

That coating is E-coat Epoxy and was lovingly applied by Mercedes to keep your parts from rusting.  It definitely won't fall off and is pretty tough stuff Honestly, If your base primer is Epoxy it doesn't matter if it is there or not.  The real beauty of E-coat is when you can dip the entire car so all the welded seams get protected against rust.

[andyburns]

I have purchased OEM panels before where i could scratch the protective paint with my fingernails.  I was always under the impression it was applied to keeps rust at bay while in storage.  I chemically stripped a oem door panel for a 108 of this coating and found spider webs of rush all over the show.  Any where the coating is compromised moisture can get in and start doing damage. Some of these panels have been sitting around for decades increasing the chances of being scratched and bruised over time.  Another giveaway to me that it isnt that flash is how easily it falls off when you put paint stripper near it.  Stark contrast to striipping of the epoxy 2k applied and then stripped.  Much thicker and harder i think.   I would chemically strip those sills, slap a rust converter on and apply the staunchest 2k epoxy you can find.  It doesnt matter how thick the coat is on the inside of the sill so i would go silly.  Surely the thicker the better.  Its a barrier at the end of the day.  Is a great feeling to think you are leaving a lasting legacy and not just tickling it up for the duration of your ownership only.

[Shvegel]

Andy,  Keep in mind that the coating on an NOS panel probably isn't E-coat but rather some air dried product. 

[Scottcorvette]

In the end I let the Gods decide.... I tried just a very small area with a bit of stripper and whatever it was on there bubbled up in no time and came off easy so I figured it wasn't anything special. I figured an ecoat would have been a bit more resistant to paint stripper, although I may be wrong there.

So it all came off, I pressure washed it , dried it, cleaned it all with scotchbrite, let it sit over the weekend to make sure it didn't go brown anywhere and then primed it all over and topcoated the inside - phew!

Now we should be ready to go. Thanks all for your input.

[wwheeler]

I have seen two types of coatings on NOS panels. One which was an E coat and very tough. I wouldn't remove that and not easy to do anyway. Then there is another which just appeared to be a primer coating. That came off relatively easy. The oldest NOS panel was the lesser coating and yes had some minor rust underneath.

[andyburns]

What do you guys think about coating bare steel with additional zinc phosphorous coating.  I did this with everything i took back to bare steel.  I believe it was done at the factory anyways.  If you chemically strip origial factory steel you can often see clear evidence.  I have read the biggest mistake when mechanically removing paint is the inadvertent removal of this layer without replacing it.  I used this product to add more zinc and also eliminate even tiny traces of rust before building up the paint layers. http://www.por15.com/POR-15-Metal-Prep_p_15.html

[wwheeler]

When you remove the protective coating no matter what it is, the bare steel will rust and quickly. So for long term, you do need a layer on bare steel that will protect and zinc phosphate is good for that.

But, you have to be really careful when you start applying paint/primer coatings. Most paint companies recommend first "sealing" the bare metal with an epoxy primer. You will need to check with that paint vendor to be sure it is OK to coat the epoxy primer on top of zinc phosphate. I am thinking most will NOT recommend that. And so you would need to sand the zinc coating off immediately before applying the epoxy primer. That is what I have always done when painting auto sheet metal.   

[Sead]

Hello,
I sandblasted all my body panels. Repro ond MB OEM as well. Used then epoxy anti corrosion primer an all parts and the car.

[Scottcorvette]

That is one taken apart car!