Combating Rust
 

I'm starting to notice a small line of rust forming on the bottom of the door, behind the front passenger wheel, just above the side skirt gasket. I'd like to get a handle on it before it gets too bad, & was wondering what I can do short of bringing it to a body shop. Any touch up solutions?

914 people are experts at dealing with the tinworm.

First, I would strongly suggest washing the car thoroughly, most especially the underside and the wheel wells. They used to spread about sixty bazillion tons of salt on the road every winter back when I lived in IL; I don't imagine it's much different now. A salt-water solution will attack any metal it finds, and rust will start. Do this after you drive on snow, and for the first few weeks after the snow is gone. Only wash it when you can keep the car warm enough for the water not to freeze again, obviously.

Next, to combat what you have, you need to know how bad it is. That means flaking off the rust that does flake off, and taking a wire brush to the surface rust. And checking very carefully around the area (and similar areas elsewhere on the car!) for paint bubbles and other signs of rust. Clean off what you can, then use Naval Jelly or Ospho or POR Metal Ready or any other phosphoric acid product on what's left. That should convert the reddish iron oxide to a stable black coating which will not spread. Then protect the surface with a good strong paint. Corolless, POR-15, or any good paint that won't crack or come off easily will work. Even regular auto paint, which you'll need if you're trying to blend in the repair to the rest of the car. (But that's another ball of wax, and may be best handled by professionals.)

--DD

Yep, I second Dave's input... you've got to prep the area, clean it, then use something like Rustmort (Rustmort is one of the best IMHO) that will chemically neutralize the area. Once that's done, you can just primer and repaint.

For the best and most cost effective repair, I'd say do all the cleaning, Rustmorting and prepping yourself... then it should be pretty cheap to have a pro-paint shop blend the paint.

Oh, one thing, the phosphoric acid based neutralizers (aka Rustmort) will eat your concrete, so you probably want to use a drop cloth/tarp under there.

What I have is a 2" line of the paint beginnining to bubble. Are you saying I should remove the bubble & prep down to the bare metal?

Yep. It's only bubbling where it's really bad. I've seen this several times. Once you start grinding away the bubbled area, you'll find it's spread to a lower degree further out than the bubble.

I do have a question, though... are you sure it's rust? Is the bubbled paint area solid? In your first post you said you saw the rust. With it being down by the skirt line, then I'd readily think it was rust. You best bet would be probably to pull the fender off (were talking about the front driver's side fender, right?), for the rust has probably propigated down under the lip area. Then you have full access and can clean it up properly. Also, it makes it easy just to take the fender down and get it repainted... no taping nor masking.

Do you have any pictures? That would help immensely.

Blk, it's on the passenger door. At the very bottom, right where it meets the side skirt.

Oh, on the door. That makes it easy to tape and paint, plus it's right at the fold of the sheetmetal, so it's pretty strong and easy to work with.

Yeah, I'd say wirebrush it, clean it, rustmort it, red-cap it (or some other smoothing filler to true up the surface eaten away by the rust), primer it, then get it painted. Should be good as new after that.

I had a body shop take a look at this rust spot this week, & was pretty bummed at what they said. First, the rust line is at the very, very bottom of the door, about 3.5" long. Upon inspecting the inside of the door, there is bubbling in the same spot just below the door panel. The auto body guy said that if he started grinding off the rust in that area, he feared he'd loose all the metal on the bottom of the door, & have to replace it. He gleefully gave me a quote of $1300 for a new door prepped, painted, & installed.

First off, I'm having difficulty believing that he'd grind through the door, even if there is rust bubbles on both sides. However, if that's the case, so be it. There's no way I can afford a new door right now, & I'd like to do something before the winter. I don't need it to be perfect, but I just don't want it to get any worse.

Question is two fold. First, is there something I can put on the surface of the rust now, to stop it from getting any worse? I found this Rust Dr. stuff on-line, but whew, pretty expensive for even a quart.
Second, what's the easiest process for getting the bubbled paint off, prepping the surface (with Rust-Mort or Rust Dr.), & painting. Keep in mind we're talking about a very small area in an inconspicuous place, that isn't seen very easily on a black car. Like I said earlier, It doesn't need to be perfect, I just don't want the car to turn into a rust bucket in 5 years. Below is a link to a pic of the rust.

http://us.a2.yahoofs.com/users/OIFHN...veas=Rust+Spot

Thanks as always

POR-15 is amazing stuff. I'm not sure what they use to make it, but you can't put the cap back on the can without putting some saran wrap inbetween the lid and the can, otherwise it will seal the can forever. It's that strong (stronger than the metal).

As for $1300, I've sold whole cars with two doors (running) for less than that...

-Wayne

I know Wayne, the shop that quoted $1,300 has gotta be a front for a crack house or something.

My thought is this, & lemme know if this would work.

1. Sand off as much of the bubbles on both sides to expose the rust; however not down to bare metal just in case the rust has weakened the surface, or gone all the way through.

2. Cover area with POR-15, Rust-Mort, or Rust Dr. on both sides.

3. Use a factory color touch up spray paint, & clear coat.

If I can get a few more years outta this without the rust coming back, I'd be happy. Plus the area it's in (bottom of the door), & color of the car, make it so it won't be so noticeable if the area isn't perfect.

One other question though, once I sand the area with the rust bubbles, how do I smooth out the sanding scratches of the painted area that will remain?

Thanks.

Wayne?

First off, 1300 for a new painted door isn't that bad. Think about it -
Remove door, door panel, speakers, window and channeling, window motor door handle, lock and and all linkage.
Order new door, body work (OEM panels are never that straight) prime,sand, paint, sand and buff, install then put everything back on the door.

Can you post or PM a close up of the rust bubbles? Use a ruler or a beer can so it will show a scale.

The first thing I would do is take the door panel off and look inside where the bubble is and tell me what you see. This will determine if is just some surface rust or something more serious. If the rust is on both sides of the panel, painting over the rust on the outside is not going much to slow it down since it will continue to grow on the inside.
As far as POR-15 - great stuff. Just beware that some of there products can be painted over and some cannot. Check out their website for all the details.

Keith

I would get a second opinion on the repair

Well, my plan of attack is this.

First I plan to sand off the bubbles on both sides of the door just down to the rust. The placement of the rust is at the bottom most part of the door, where it is not hollow, just folded metal from outside to inside.

Second, apply POR-15 to both sides of rusted section, all to dry, & do the appropriate dry\wet sanding with assorted grit papers.

Finally, apply this factory color spray paint to the surface, & follow it up with the corresponding clear coat.

Again, I'm not looking for a show quality repair. I want to keep it from getting any worse, & remove the bubbles. I think the placement of the damage is in such a spot where my repair will be somewhat inconspicuous.

Thoughts.

Sounds like you have a good solid plan

Well I was able to flake off the rusted portion of the lower door panel, & fortunately for me, there was no damage through to the other side of the door. The sanding & prep was pretty easy. The por-15 seemed to work good as well, & now I'm on to the painting process.

My biggest concern was feathering the touch up into the existing paint. I obviously didn't want to brush into an area this big, & I don't have a compressor, so I've decided to use this aftermarket touch up that comes in an aerosol spray can.

https://www.automotivetouchup.com/spray_paint.asp

I got some of this in my OEM BMW color code, & also in a clear coat variety. After I complete the repair I'll post 'before' and 'after' pics.

I've also start to see another small paint bubble forming on my rear trunk panel, just above the bumper. I've gotta say, I'm very surprised to be finding this much rust forming on a '97 model year BMW. Every since I first I noticed the first rust bubble along the door, I've been consciencely looking at that spot on other Bimmers to see if it's a consistent issue; however most e36 & newer cars seem to be rust free. I know the Chicago winters can be rough, but I can't fathom why I'm having such an issue with rust. Any thoughts?

Super:

The rust is from the the outer door skin folding over the inner and how the two are joined. This seam, although covered very well by BMW, traps moisture from the inside as it gets past the seals.

You'll notice that your door has a couple of holes [typically one in front and back] that allow for water that gets past the outer window sill seals a place to escape. This is how it is on my E30 and several other BMWs I have seen.

You might want to replace your outer window seal [one that scrapes outside of sindow when you lower it] as well as doing all this work.

The doors on my E30 are also rusting exactly where you mention and the factory installed sealer / caulk bead is flaking off. I have to face this repair as well and being a fan of POR-15 will be using it to do so. *note that POR-15 doesn't like UV and should be top-coated with something else [aerosol paint to match and clear] like you did. Have used POR-15 on the underside [subframe, unibody, etc...] with good results.

Good luck.

hi there,

While agreeing with the comments on this so far, there is another thing to do that prevents spreading of rust any further. Just get some "fishoilene" (sprayable fish oil) and apply liberally to all seams and crevices and box sections that might attract moisture and rust. The fishoil spreads into crevices etc and excludes air and water == rust stops. It sounds too good to be true but I've done it on many bubbling doors etc and it does work. The bubbles stop progressing. Of course, I agree that the only way to get rid of it is to replace metal and repaint, but you can delay progress of rust and prevent more starting...

If you fix the rust as per the suggestions above then some fishoil in the door will stop it coming back.

There are other mixtures of waxy materials etc that are probably effective also, I have just used fishoil.

I'm in the middle of saturating a 2002 with the stuff - a good test. I'm also going to try POR for the first time, it looks a very nice product.

Finally, I also think it is strange that a later E36 is showing this door rust, maybe it is the road salt. We don't have that problem here.

Good luck,
Chris (Brisbane Aust)

They do spread a bazillion tons of salt on the roads in Chicago at the first dusting of snow, but since I noticed the bubbling, I've been consciously looking at other e36 lower doors panels to see if the same problem exists with others. I have not seen one with this issue any newer than an e30. Kinda ticks me off.