Noob needs advice for rust around sunroof.
 

Just bought a '82 300SD earlier this week and its got a substantial amount of rust around the lip of the sunroof. Its to the point where its flakey and you can break bits off pretty easily. I'm just looking for some general advice on fixing it. Most of what I've read about treating rust involves sanding the rust off, then priming and repainting. The problem here is that if I sand all of this rust off I suspect i'll pull at least 1/2 cm of of metal away. Is that what I want to do? What do I do afterwards? Just try to fashion bondo around the lip? Any advice is appreciated, including a "dude, you have no idea what you are doing, take it to a body shop ;)" Here are some pics.

http://www.speakeasy.org/~pjohnson/benz/rust2.jpg
http://www.speakeasy.org/~pjohnson/benz/rust1.jpg

well
 

it looks like when the car was repainted they sanded too much off there. i would sand it down to the bare metal and put rust binder on the area. then sand again and bind again. then i would sand once more and then apply the thick primer paste. then sand again and prime. then apply paint. this should hold the area for quite some time.

tom w

Speaking of rust binders, I read about POR-15 on another MB site, and used it myself for some rust in the corners of the sunroof. If you go to the POR-15 website, you'll see they have different formulations, and some of them are thick enough they'll fill in minor low spots.

I think when I sand its gonna pull largish chunks of rust/metal out. Will the rust binder and primer paste help to compensate for the everything I sand away?

I second the POR-15 route. I am doing this on my cruiser right now.

Works awesome.

Just grind or sand, paint with por-15 and then use there version of filler. after use a primer and paint.

should last a long time more.

check out por-15. it is not a gimick. I have used this stuff on my frame and fenders.

I am sold. Its like powdercoat in a can. it blocks oxygen and moisture from the surface. Thats how is works.

Also it likes a bit of tooth to grip to. So seasoned metal works best, little rust or nice and sandblasted clean. Marine clean and then metal ready. Let dry, Por-15 it and then use filler.

Good luck. That rust isn't so bad. I bet a week end would clean it up if you do the POr route.

Cheers

I have a slightly different recommendation that is much more involved. I would obtain a roof section of the sunroof from a junkyard car. Since very few of these cars rust in this area it should be easy. Once that is done the rusty part should be cut out and new virgin metal should be welded in. After that standard body shop procedures should be used to refinish. That includes priming with zinc primer. I think this is the only way to prevent rust from coming back. This also is dictated by the overall condition of the car and its relative value to you.

Another option from the POR-15 website:

POR PATCH™

For years our customers have asked us for a thicker version of our world-famous POR-15® for filling seams or holes. Here it is! POR PATCH™ is, quite literally, POR-15® in a tube, and like POR-15® it dries as hard as a rock, remains flexible, and once dry is totally impervious to fuels and solvents. It's so tough it actually adds strength to weakened metal. And it won't absorb moisture and swell like conventional body fillers. Try it yourself, it's incredible!


Available in Black or Pearl White

5oz. Tube - $15.00

I just called POR-15 and they recommended the starter kit for $15 which includes the marine clean, metal ready, and the POR-15. They were super helpful. They told me that any remaining uneven pits after the POR-15 application could be filled with bondo and then primed and painted. Nice. Thank you to everyone who responded.

Good luck, and if you could, post a picture of your results.