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Anyone else noticed any surface rust on inner arches?


Buggyjam

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Just exploring the inner arches on my car at the front. There’s a few areas of surface rust here and there on the inner arches. A couple of circle spots where the spot welds are that I suspect are more than surface. Some areas are still yellow paint but a lot looks like bare galvanised whet paint has come off. I suspect the surface rust is where the galvanised has failed or taken stone abrasion. The fact the paint is missing in quite large areas near the suspension mounts tells me looks like the paint has been stoned off over time. Doesn’t look like there was ever any waxy underseal applied at the factory (looked at a 981 at the opc and it had it) just paint.  I’ve got a stack of Bilt Hamber stuff sitting and waiting and going to attack it all. 

 

Heres the workflow I’m planning:-

 

Jack each side up and do the following

1/ Inner arches removed

2/ degrease using Bilt Hamber surfex

3/sand areas off using course grit.

4/ use Bilt Hamber Deox C gel for 24 hours under cling film 

5/ scrub, rinse with water then paper dry and use misses hair dryer to make sure water gone

6/ apply two coats of Bilt Hamber Electorox zinc primer, leave for 96 hours for full cure

7/ Apply Bilthamber Epoxy mastic anti corrosion coating leave to cure for a day or two

8/ top coat with speed yellow using a brush (its out of sight up under arches)

 

hoping that sorts it. Big prob is need temperature over 10 degrees for some of it to cure.

 

anyone else noticed any rust at all on their inner arches? 

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My rusty calliper bolts have remained rust free since applying some Kurust and a permanent marker pen. Looks like you're going overboard! Can't blame you for that.

 

On Car SOS, Ed usually sprays any restored steel with "stone chip" - I've often wondered what's in it? A magic solution perhaps?

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Just now, DJMC said:

My rusty calliper bolts have remained rust free since applying some Kurust and a permanent marker pen. Looks like you're going overboard! Can't blame you for that.

 

On Car SOS, Ed usually sprays any restored steel with "stone chip" - I've often wondered what's in it? A magic solution perhaps?

 

Ed is the man,

 

i think youre right about overboard, that occurred to me. I’ll tell you how my thoughts came on it. Prob the wrong thinking. Originally I was going to just spot sand and prime the rusty spot welds or panel edges that are showing the surface rust. Then I stepped back and had an overall look. There’s quite a few areas that are just showing small areas of rust, just small. Enough you can see the galvanising is starting to fail a tiny amount here and there. And that’s what stuck, if rust is there, it’s in and past the galvanising. And then I realised with large areas on the inners are now paint free and just bare galvanised steel so it prob was going to degenerate slowly with rock impacts. So I thought I’d scrap trying to patch and hopefully do a big removal job with some protection thrown on top and halt it in its tracks.

 

The big dilemma I’m having is when I sand the area to take the zinc primer of course I’m essentially damaging galvanised layers that wasn’t yet failed. So it better be a good job. 

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Google "galvanising primer." I've no idea which to use, but it occurs to me that you may be able to re-galvanise the areas you're un-galvanising?

 

I'm guessing the Bilthamber Epoxy mastic anti corrosion coating is like an undersea which will absorb rock impacts without damage under?

 

Ah... here we go... According to Bilt Hamber, after the Electorox (6) and before the Mastic (7) "galvanised steel should be etch-primed with etch-weld self-etching primer."

As here: https://www.bilthamber.com/which-paint-or-coating (3rd from last sentence).

 

2 here may help too: https://www.galvanizing.org.uk/painting-galvanized-steel/ as may the rest of page/site.

 

Fair play to you for having a go at this. I can imagine you must have done hours of confusing research trying to find the correct process? What we need is an "expert" to come along and dissect your plans. That is NOT me!

 

 

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15 minutes ago, DJMC said:

Google "galvanising primer." I've no idea which to use, but it occurs to me that you may be able to re-galvanise the areas you're un-galvanising?

 

I'm guessing the Bilthamber Epoxy mastic anti corrosion coating is like an undersea which will absorb rock impacts without damage under?

 

Ah... here we go... According to Bilt Hamber, after the Electorox (6) and before the Mastic (7) "galvanised steel should be etch-primed with etch-weld self-etching primer."

As here: https://www.bilthamber.com/which-paint-or-coating (3rd from last sentence).

 

2 here may help too: https://www.galvanizing.org.uk/painting-galvanized-steel/ as may the rest of page/site.

 

Fair play to you for having a go at this. I can imagine you must have done hours of confusing research trying to find the correct process? What we need is an "expert" to come along and dissect your plans. That is NOT me!

 

 

 

Thanks DJMC really appreciate the help on it. You’re right I ended up researching for a long time lol! Bilt Hamber seems to be considered the best stuff for all this from what I can gather. 

 

The electrox is one of the galvanising primers. It’s about 90 percent zinc I think. The small tin weighs a ton lol! It sets up a galvanic circuit basically, As you say the epoxy mastic is a hard layer that goes on top and acts as protection. Prob I’m having is I thought electrox could be applied to roughed galvanised steel (albeit damaged in areas) but then I’ve read etch primer should be used. Prob is etch primer is pretty useless on the corroded areas where there is no galvanising and not a good base for corrosion protection (its porous). You’d want electrox on the damaged bits. I’ve read on other forums guys have repaired galvanised sections using electrox as a base. It’s all down to making sure it sticks and bonds. From what I gather electrox does have self etching qualities but needs a rough surface. I’m going to ring Bilt Hamber tomorrow and ask them. 

 

 

 

Just wondered if anyone else has noticed small areas of corrosion, even surface rust on their inner arches? You really have to look quite closely as it’s buried. Daresay most wouldn’t worry but I want to keep the car a long time really. Had a bmw that went in this area eventually and know you kind of have to nip it in the bud once stones start punching through the galvanise.

 

like you say an expert would be fabulous if any are reading this ha!

Edited by Buggyjam
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Just realised in my original post there’s a major typo! 

 

Step 1 should say “plastic inner arch shields removed”

 

its the metal inners arches that are the problem (areas near where the suspension mounts to at the top. I wish you could unbolt them lol!

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Update.

 

I rang bilthamber and too, some advice on this. 

 

Just to recap. Inner arch has half of it still painted, half of it bare, rust free galvanised where stones have taken the paint off, and a couple of spots of dark rust where the spot welds are and the galvanised has failed.

 

The plan is

 

1/ degrease entire inner arch 

2/ course sand the rust areas to remove much as possible

3/ apply Deox gel for 24 hours in entire inner arch, then agitate and remove with water then dry

4/ pain Electorx zinc primer only on areas where galvanised has failed and feather into the galvanised area

5/ apply etch primer to the bare galvanised sections that were rust free

6/ coat inner arch with epoxy mastic

7/ once set hard top coat with paint

 

This should reprotect the inner arch. Prob is electorox won’t adhere bond to galvanised steel. And you don’t want to sand the entire inner arch and remove galvanised that wasn’t rusty, so you need etch primer on those areas. The other issue is the half of the wheelarch that still has paint on can’t reallt be painted over with either primer so I’ll have to feather those areas in and then epoxy mastic the whole area. 

 

One thing ive learned with rust is however small, don’t leave it. Once it’s past the galvanise there’s nothing stopping it tunnelling through to the other side. As mentioned, happened on my BMW in the same area.

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1 minute ago, PMGPete said:

Potentially worth mentioning to Porsche as afaik they have a 10 year anti corrosion guarantee

Thanks Pete. I’ve explored it and think it’s no joy on that one, as it’s not holed through. The other thing is their corrosion warranty is invalid if paint isn’t repaired. The paint is missing on the inner arches due stone chipping. Prob been like that for ages. It’s a design flaw, whether they didn’t put on underseal there I’m not sure. Could try that angle. I’ve also noticed I’m missing the second inspection stamp :(. I didn’t spot this when I bought it.

 

im still off down the opc to try :D. I’m betting this is mega common but you kind of have to look for it really. Only found it by accident when looking at my top mounts. 

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I used to own a Fiat X1/9. It was 20yrs old? About 84% plastic filler, i swear it left an orange stain on the road every time it rained. I loved that old pile of crap though. 

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4 hours ago, graham.reeds said:

When I bought mine it had a few spots in the arches - all smaller than my pinkie nail.

 

Got them fixed as part of my preventative maintenance when I first bought it.

IMG_20171014_130320.jpg

IMG_20171014_130301.jpg

 

Cheers Graham. Mine had a few of those down to metal when I got it, only tiny and luckily only one faintly corroded. Got the area fixed. Managing to keep on top now with regular battle damage touching in doing it myself with a Porsche stick. Areas on mine are near the spring mounts on the arch. 

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