Is this corrosion, or an intentional surface treatment?

[stormforge]

I'm doing some paint work on the nose of my '89 Syncro right beneath the corners of the windshield. It seems like there's red paint on top, then grey primer, and then a hard black coating under the primer? See the smooth black areas in the picture:

In the lower areas the paint and primer seem to have been applied *very* heavily and are peeling off as a thick sheet leaving the black coating underneath. The black areas certainly seem like they might be some sort of intentional coating -- they are smooth and tight -- but I haven't seen anything like that when working on other areas of the van.

Is the black coating a pre-prime metal treatment, or is it some sort of oxidation under the primer? Should I leave it in place and prime on top of it -- or should I try to strip paint back until I don't see it any more?

Thanks!
-Bill

[Red Beard]

That looks like the coating I've seen on new/aftermarket replacement body panels in the past.

E.g.
http://www.autopartswarehouse.com/search/?Ntt=Fender

[stormforge]

Interesting! I have a pretty good history on this van and there's nothing at all to indicate a major repair -- but who knows? All the nose panels look like this...

More evidence:

A brazed (or silicon-bronze TIG?) seam -- this appears both sides. Could this be how they put the van together at Steyer? I have heard that, for some Syncros, they received panels from VW and assembled the bodies themselves? Or is this definitely a repair?

Thanks!
-Bill

[Signalocity]

[bluebus86]

the dark area is a primer, so is the lighter area. it appears you had an adhesion issue with the red color? why, was red applied super thick, was prior film contaminated, or not compatible? what ever it is Id think youd want to remove all the paint down to below the adhesion failure area. Note the entire van may not require this level of sanding, only the spots with adhesion issues if need be. just dont paint over adhesion issues, ever!

also be sure to degrease, dewax, desilicone the paint prior to sanding, if not you risk curling, trapping the contaminates into the top layer of paint you leave after sanding, that can cause a paint defect known as a "fisheye". A fisheye is a pin point area that the paint wont wet, it forms a little crater in the paint down to the trapped wax, oil, silicone particle. so clean paint prior to sanding of wax, silicone, oils to prevent fisheyes.


now you do appear to have rust going on in the window seal gutter, address that for sure. besure to use a two part epoxy or urathane water proof primer to help prevent rerusting, specially in areas that pool water like the windows areas, seals etc... of course remove the rust first.


good luck, neat project, wish i had the energy for that!
_________________
Help Prevent VW Engine Fires, see this link.....Engine safety wire information

Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022