rust spots

keven · 04-19-2006, 03:30 PM

well my other problem is that i have some rust appearing and i want to take care of all of it. Is there a DIY to this or can anyone help me out with how about i do this and wat do i need to know im a rookie at this lol. thanks

Justin e36 · 04-19-2006, 04:01 PM

where are the rust spots.. is it just paint bubbling up?

SUPERCHARGED · 04-19-2006, 05:49 PM

i have the same problem, pain is bubbling up on the top edge of my hood.on like a 3 inch spot. what can i do?

bmdbley'sBro · 04-19-2006, 07:44 PM

If its someplace invisible ( bottom of a fender behinf the wheel) DIY is great.

But start talking about hoods & highly visible parts, it's harder to DIY decently.

Wire brush the rust away completely, fill if needed, anti rust prime
then apply touch up paint.
Por-15 ontop of that if needed or worried

blending areas of new & original paint is hard , so is color matching
thats why they always paint a larger area with a spray gun

Justin e36 · 04-19-2006, 07:47 PM

yeah.. don't use touchup.
I don't wire brush.. I use sandpaper, then I fill it with bondo, sand smooth, mask the surrounding area... prime, paint, and clear. Always with a spray gun....

DbIiRrTdY · 04-20-2006, 02:26 PM

i find with sanding the rust off the metal I can never really get into the small divits of rust with out grinding a significant amount of metal - is there a chemical you can put on the rust to eat it away then fill with cheese, sand prime and paint?

BMW_7 · 04-20-2006, 02:49 PM

First I completely sanded down the area to the bare metal, then I used rust removing liquid and I stuck it on the spot (cotton ball and tape it on overnight) to get all the rust out. After that was done, I put on clear and touch up paint. (This is in the area behind the wheel well).

So in the end, for a whole year it was perfect, no rust, until just now it started coming around the edges....Rust will always come back, no matter WHAT you do, maybe not for a year or two, but it will always come back. The best thing to do would be cut off the metal and weld new one in... Even still, it can rust at the welds..

Nothing you can really do about it...

RMKBMW · 04-20-2006, 07:24 PM

On the topic of rust. I was just wondering if anyone had thought of installing a sacrificial anode system..

Justin e36 · 04-20-2006, 07:45 PM

Rust will not come back if properly taken care of. Rust oxide's prime inhibitor is oxygen. When combined with an electrolyte (water), it creates a weak acid. Salt-water will make an even stronger acid, which will accelerate the oxidation. The acid disolves the iron, while the water breaks down to hydrogen & oxygen. The oxygen binds into the metal, creating the iron oxide.. (also known as rust.)

Typically covering up a rust spot with a touch up brush does not seal the metal, and a lot of the time the rust is actually forming on the other side of the metal. For example, the rear fender arches have a lip on them, the inside of the lip gets pelted with stones which break into the metal. Sand, salt, and water builds up on the lip which eats through the metal... and on the outside, we see rust bubbles forming under the paint. Sand this down, and fix it all you want.. the rust will continue to come back, since the cause is on the other side of the metal.

This is why undercoating or rust proofing your car and body's panels can be so beneficial.

RMK, unfortunately anodes won't work on our vehicles for a few reasons. One is the quality of steel BMW uses does not conduct electrons well enough for a galvanized anode to be effective. The second reason is our vehicles do not have contiguous metal. There are rubber bushings, and plastic brackets that get in the way. Anodes work best on vehicles that were designed for them, or unibody structures such as boats.

BMW_7 · 04-20-2006, 08:20 PM

Quote:

Originally Posted by Justin e36

Rust will not come back if properly taken care of. Rust oxide's prime inhibitor is oxygen. When combined with an electrolyte (water), it creates a weak acid. Salt-water will make an even stronger acid, which will accelerate the oxidation. The acid disolves the iron, while the water breaks down to hydrogen & oxygen. The oxygen binds into the metal, creating the iron oxide.. (also known as rust.)

Typically covering up a rust spot with a touch up brush does not seal the metal, and a lot of the time the rust is actually forming on the other side of the metal. For example, the rear fender arches have a lip on them, the inside of the lip gets pelted with stones which break into the metal. Sand, salt, and water builds up on the lip which eats through the metal... and on the outside, we see rust bubbles forming under the paint. Sand this down, and fix it all you want.. the rust will continue to come back, since the cause is on the other side of the metal.

This is why undercoating or rust proofing your car and body's panels can be so beneficial.

RMK, unfortunately anodes won't work on our vehicles for a few reasons. One is the quality of steel BMW uses does not conduct electrons well enough for a galvanized anode to be effective. The second reason is our vehicles do not have contiguous metal. There are rubber bushings, and plastic brackets that get in the way. Anodes work best on vehicles that were designed for them, or unibody structures such as boats.

Well thanks for the explanation, now I know what I gotta do.
I did undercoat it, but only the year before last year.

Dunno if I'll have time to strip that area apart though, I gotta give it a try.

djcontra · 04-20-2006, 08:53 PM

dont forget to treat the bare metal with rust converter before priming and painting. It will prevent oxidation of the metal (which even atmosphere or the oils on your skin will start)

M3ti Compact · 04-20-2006, 08:54 PM

so...heres what I got...

1. Sand
2. Rust Converter
3. Primer
4. Paint
5. Clear

anything else??

Justin e36 · 04-20-2006, 10:41 PM

Quote:

Originally Posted by BMW_7

Well thanks for the explanation, now I know what I gotta do.
I did undercoat it, but only the year before last year.

Dunno if I'll have time to strip that area apart though, I gotta give it a try.

It's a time consuming process. When I stripped my car and painted it last year, I sandblasted and undercoated the back of the fenders, hood, trunk, rear quarter panels, all inside the trunk, etc. etc... there were some places I couldn't do, like the A pillars. Yesterday I finally washed the car, and guess where I found some rust bubbling back up?... That's right, the A pillar.

.. I'm going to have to pull out the windshield again to fix it properly, maybe this weekend.

Quote:

Originally Posted by M3ti Compact

so...heres what I got...

1. Sand
2. Rust Converter
3. Primer
4. Paint
5. Clear

anything else??

I would personally wet sand with 600 or 800 grit after priming, and after the first coat of paint. I've never used rust converter before, so I'm not sure how it works with painting or priming...