Hoping for suggestions on fixing minor rust

[m3f_ReturnToS54]

I've been inspecting my newly acquired coupe for rust, and I found two minor areas that I suspect are the result of a previous owner running larger wheels/tires with a lowered suspension. One area is on the inner lip of a rear quarter panel near the point where it meets the rear bumper, and the other is on the inner rear wheel well, which appears that it may have at one point been trimmed to address a rubbing issue.



The inner lip of the rear quarter panel is the area I'm most concerned about. Using a dremel to sand it down and remove the rust like an easy solution, but I don't want to create too much heat and damage the painted side of the quarter panel. Perhaps I should sand it by hand?



On the wheel wheel rust, I'm thinking dremel or drill with a wirebrush attachment, and then seal it.



Any other suggestions?

[m3f_Braymond141]

That is hardly "rust", this is light surface corrosion. Just dremel it off, which will take no time whatsoever, prime (or SEM EZ-Coat), and underseal. You're over thinking this with all the heat generation and such. You don't even need to touch this if you're in a no salt state either...

[m3f_ReturnToS54]

Thanks for the reassurance. Fortunately, the car is in a dry climate.

[m3f_zhp43867]

Echoing what Braymond says, dremel it (with the sanding attachment) and use any "stop rust" primer and undercoat.

[m3f_frbz]

How well will POR 15 work for this?

[m3f_Braymond141]

How well will POR 15 work for this?

Why?! This isn't a blown out rust issue. Leave that to the Brits and rust belt owners. He should keep it factory original.



SEM EZ-Coat in the matching factory color (hidden by the gray dirt shown), and then add any underseal if you want, them recolor again with EZ Coat.



Like this;

[m3f_zhp43867]

POR 15 will work *better* as there's almost no shot light corrosion like that could continue after. However, it won't look factory and it's harder to work with for a proper finish. I still second Braymond's proposition in this instance. You can find corrosion like the OP pictured on many five year old F30s.

[m3f_ReturnToS54]

Thank you for the tips. I took a dremmel with a sanding brush attachment to the affected areas and removed the surface rust. I then coated it with four layers of primer. After I finished up the passenger side rear I checked the driver side rear wheel well, and found that it was in worse shape. There was rust higher up inside the well where a tire had rubbed, and the lip was in bad shape. I was able to sand down the rust spots, spray them with primer, and use rubberized wheel well sealant on the arch. However, in the process of doing this I noticed bubbling running over half of the underside of the wheel well lip. I've attached a photo. It appears there is a lot of rubber "tire dust" on the inside of the lip, which I suspect is from a tire rubbing on the arch and then pieces of the tire falling down inside of the lip. My guess is this then trapped water, which has led to rust. Any thoughts on the best way to handle this area on the underside of the lip where bubbling is occurring? Really trying to avoid a trip to the body shop.

[m3f_Braymond141]

There's no issues in either of those photos. The second photo is just showing the factory e-coat and seam sealer.

[m3f_ReturnToS54]

That would certainly be a relief if it is nothing to worry about. So you don't view these bubbles as being a sign of rust?

[m3f_zhp43867]

Looks like rust to me... but I'm not an expert. Primer is also not the best idea for rust repair as generally it is not meant to be a top coat- meaning water will permeate it quicker than if you use any sort of top coat. Not sure what type of paint Braymond mentioned but you may want to give that a shot. If you top coat primer with undercoat that's fine.

[m3f_ReturnToS54]

Thanks for the advice on the top coat. I'll go over it with a rubberized sealant.

[m3f_Braymond141]

I would not say that is rust. That area of the wheel arch is not particularily well finished. All 3 of my E36 M3 here have similar bubbles/imperfections under the paint.



Don't stress it...

[m3f_Earthwormjlm]

Why?! This isn't a blown out rust issue. Leave that to the Brits and rust belt owners. He should keep it factory original.



SEM EZ-Coat in the matching factory color (hidden by the gray dirt shown), and then add any underseal if you want, them recolor again with EZ Coat.



Like this;

Just curious, why don't you like POR 15?