Fine edge of rust on one wheel well

[xdewhy]

I recently noticed a fine edge of rust on the wheel well. Not sure how this happened, but what's the best way to fix this / prevent it from spreading? Is this something I can sand, prime & paint it myself easily?

Picture here: https://imgur.com/a/0jK2vLP

[Thumper3]

That is pretty bad and has been rusting for some time, see the bubbles? That's rotten metal. Is that the fender or the quarter panel, hard to tell. If it's the fender, it's an easy fix to replace it although not cheap. If it's the quarter panel that's bad. I've been in auto body repair for 21+ years, we don't call rust the cancer of the industry for nothing.

You CAN try to fix it yourself as a bandaid to keep it from getting majorly worse for a few years. How good that looks will depend on your skills and patience.

Confirm if it's the fender or the quarter and I can give you some more specifics.

[xdewhy]

Yes, this car already had the marks there before I bought the car (1.5 years ago) guess then it started to rust over time and I only noticed a couple days ago.

The rust is located on the passenger side right wheel arch, right in the middle of the wheel well.

My plan is to bandaid fix it for now and try to prevent further damage for a couple years.

[1killera4]

Yes, this car already had the marks there before I bought the car (1.5 years ago) guess then it started to rust over time and I only noticed a couple days ago.

The rust is located on the passenger side right wheel arch, right in the middle of the wheel well.

My plan is to bandaid fix it for now and try to prevent further damage for a couple years.

There is no real "Band-Aid Fix" for rust. It doesn't stop unless it is removed completely form the substrate that it is growing in.

[Thumper3]

Yes, this car already had the marks there before I bought the car (1.5 years ago) guess then it started to rust over time and I only noticed a couple days ago.

The rust is located on the passenger side right wheel arch, right in the middle of the wheel well.

My plan is to bandaid fix it for now and try to prevent further damage for a couple years.

So that's the REAR wheel arch (quarter panel), and yes that is really bad. Basically, that is the outer "skin" panel, inside the wheel well it wraps around the inner panel edge. So based on the bubbles the inner panel is almost certainly rusting out as well requiring replacement of it as well. The only cure for rust is to replace the panel, you are talking about easily a $8k-9k job depending on the local rate for body and paint work.

The problem with the bandaid is rust is not just a surface problem, it is in the metal (again, cancer) so even once you remove the rust you can see it continues to grow inside the metal under the repair. In this case you can't even pretend to attack the rust since it is at that double panel seam in the wheel arch. I promise you there is rust between the two panels.

So, to slow it down and prevent the bubbles becoming a full blown hole in a year or two you can sand down the paint and feather down to bare metal, remove all the rust you can see. The issue is once you do this you WILL have some small holes already (that's what those bubbles are), so you will have to fill them after you treat the metal as well. You will want to sand the rust on the inside panel flange as well and apply the anti-rust coating there too. Then cover the bare metal with a product like POR15, make sure to get into those tiny holes it might even lightly fill some of them. Then use a high quality body filler to fill in the rest of the holes, this is NOT a proper repair method principally called "cave and pave", body filler should never normally be spread more than 1/8" thick but again, this is a temp repair at best. Sand that, apply primer, then apply color coat, then apply clear coat. Since you likely will not be taking off the bumper, tail light, ect and applying the clear to an edge either there will be either a noticeable line where you mask off the clear, melting or blending the clear coat is a pretty advanced method for avoiding this but you can wet sand the area and polish it and should look decent (better than rust bubbles anyway).

If that broad description of the task ahead of you did not scare you off it will take you the better part of a day or two and will need to make a shadetree paint booth in a garage with drop clothes at least.

If all of that sounded daunting, visit some body shops for quotes, not all body shops will even tackle rust repair due to repair quality and warranty but certainly will find some that will. Will likely still be $2-3k, and it might buy you a few years before the bubbles come back depending on where you live (cut it in half if you live and drive where they use salt in the winter).

[xdewhy]

Yes, that is what I am planning to do. I know now that you can't "fix" rust this way, but it's already rusted there so I'd rather do something rather than nothing. My buddy has most these supplies (sanding paper, POR15 & filler. I bought primer, color coded paint & clear coat) so I'll plan for a solid day to make sure I do it properly.

After I fix it, I guess the best way to slow down the underlying rust would be to keep this wheel well clean (especially in the winter months)? Also I don't know if it's worth mentioning, but the car came with a rust undercoating.

Thanks for your help.

[Zee Dgerman]

already rust on a B9? are you sure the car wasn't in an accident?

[Thumper3]

Also I don't know if it's worth mentioning, but the car came with a rust undercoating.

Oh, did the salesman get you on the hook for the TruCoat? :D Fargo reference. LMAO

And yes, best to keep it clean but that goes for the whole car really. If they throw salt on your roads it is vital that you are meticulous in keeping it cleaned off regularly.

already rust on a B9? are you sure the car wasn't in an accident?

Very good point, although if done by the previous owner not much to be done now. Although it could be worth a warranty claim with Audi (about to go through that with VW on the Golf R, spot of rust inside the door jamb and we'll see how that goes. I was told it's usually not good lol). Still, might be worth throwing it at the wall and seeing if they cover it. If they say no you're no worse off.

[xdewhy]

Yup, it has been in an accident before. I won't make this mistake again!! I'll try asking the dealership. I agree with you though, won't hurt to ask.

The rust undercoat was something they added on for free as an extra

Anyways... appreciate the comments haha.

[Thumper3]

Yup, it has been in an accident before. I won't make this mistake again!! I'll try asking the dealership. I agree with you though, won't hurt to ask.

The rust undercoat was something they added on for free as an extra

Anyways... appreciate the comments haha.

Ah, if it was in an accident and that was where the repair was unless that repair was completed by an Audi Certified body shop they won't cover the warranty so wouldn't waste the time. That sucks.

[1killera4]

Sell it. :)

[xdewhy]

Ah, if it was in an accident and that was where the repair was unless that repair was completed by an Audi Certified body shop they won't cover the warranty so wouldn't waste the time. That sucks.

Yea, I contacted Audi Dealership and their first step is for me to come in this week so they can take pictures. I'm not sure if the previous repair was done in an Audi Certified bodyshop, so we'll see what they say.

While I wait for their decision, what's best to keep that area clean? I'm sure washing that rust area diligently will help somewhat? Snow has basically fully melted so the roads are not too dirty

[Thumper3]

Yea, I contacted Audi Dealership and their first step is for me to come in this week so they can take pictures. I'm not sure if the previous repair was done in an Audi Certified bodyshop, so we'll see what they say.

Lucky, I called the VW certified shop my dealership told me to contact to see about my Golf R and they said they don't do any rust repairs. LMAO I was like it's for a warranty and they were like nope, sorry. Have to call VWoA now to be like wth. lol

While I wait for their decision, what's best to keep that area clean? I'm sure washing that rust area diligently will help somewhat? Snow has basically fully melted so the roads are not too dirty

Wash it AND dry it, preferably with a dryer, make sure to get all the moisture off.