Rust Spot Fix Question

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e9coupeMA

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Pulled my windshield out and gasket. Under the gasket toward the at about its midpoint I found a small but fairly severe rust spot. About the size of a quarter.

Can anyone suggest a good strategy for me to mitigate the spread of the rust? I have still have some malaga red paint.

Any suggestions will be appreciated. The auto glass guys come in a few days and I want to repair before their arrival.

Jamie
 
Agree, the best fix is cut, weld, grind, prime, paint. We have all learned that. New member perhaps was surprised at what he saw and is hoping for some miracle spray and go, rust terminator kinda fix. Not saying I have not tried that in some cases, not on my Coupe of course, but where this rust is situated, it really must be cut away and replaced with new. There are definitely more steps and will not be done before auto glass appointment, but this is where ownership really starts. These Coupes really deserve the best in rust remediation. Testimonials will surely follow. Good luck with the repair, perhaps photos and describe how it goes? Mike
 
guys. thank you and I get it. here are some pics to me is seems so small. but, I guess I should listen to the elders. tale a look at the pic. it's small. you guys really think it deserves a cut, weld, grind and repaint of the whole rig? if thats the case then would it be a chrome off full media blast, etc. etc.?
 

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also, here is another pic of a separate issue which I would like to think is a failed paint issue but you can see a small about of rust.

Let me know your thoughts on that and a big thank you for all you passionate e9 guys.
 
You have a few options…
  • 1) Cut out weld a new section in…

  • 2) Wire brush on drill and clean off as much rust as possible – treat with rust killer – prime with a high zinc content paint.



 
If you can get it over in the states try Bilt Hambers Zinc Primer. I've painted all bare metal surfaces on the e9 in that ( 2 thick coats) and with their weld through etchweld primer at any spot weld points. 1L weighs approx 8kg, when dried it forms essentially a cold galvanised coating.

Painted their zinc primer onto a rusty cast iron stove left outside for decades. When I say painted, I filled the leftover paint cup up with thinners and mixed the dregs of paint up to clean out the brush and brushed a single extremely thin layer directly onto the surface rust with no prep. 1 year later and no rust has come through
 
My take is that it all depends on how deep the rust is. Difficult to see on your pic how deep it is.

If it's through, even just a pinhole, then for sure it is a welding job.
A pin hole is sometimes just a half mm, or even less; i drill these to 5 or 6 mm and then weld it shut. If the hole is larger, or the area really thin, then you must cut out a larger bit.
If its just surface rust then ot depnds how much thickness you lost. I use one of the thin belt sanders to sand the rust out. Put a large light on it and inspect from 5cm close to check if you see any brown specs. Remove any spec that you identify. If you're lucky you will have 0.6mm left of the 0.8 mm sheet thickness. Thats enough to paint over.
If you sand through the rust, then you haven't lost any good steel, it was rust and must be replaced anyway.

I also use a carbide cutting tool on an airspindle to form welds (and steel). Easy to use for small details as these. Take care of the chips flying off; the're raisor sharp.

Mind you that when you weld, there is also a backside to treat. After welding i always treat the backside. Paint or wax, but at least do something or it will be back in 10 uears rusted from behind.

I had holes in the rear window frame, not unlike your pics, but a real hole. First thing i did is drill through (~6mm) , including the opposite sheet forming the channel/cavity. Then weld and grind flat. With that second hole i could spray paint inside the cavity that forms the window frame, to the backside of the plug welded hole.
 
I was picturing something a lot worse. Always sand before grinding to see if you can save metal. Grinding can make a small simple weld a lot more difficult with thinner medal, etc.
 
You guys all are great. Thank you. can you voice any opinions as to what you think might be going on here? I almost feel with the pimple like paint that it's a paint failure issue but the little rust spot make me think it maybe something coming up from below. Thoughts?
 

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Stick your hand up there. There should be an undercoating, if that is coming up, then you have an answer.....there is kind of a shelf up there too. Nice for gathering sand and dirt.
Hope Pandora's box stops here for you!
 
eriknetherlands said:
My take is that it all depends on how deep the rust is. Difficult to see on your pic how deep it is.

If it's through, even just a pinhole, then for sure it is a welding job.
A pin hole is sometimes just a half mm, or even less; i drill these to 5 or 6 mm and then weld it shut. If the hole is larger, or the area really thin, then you must cut out a larger bit.
If its just surface rust then ot depnds how much thickness you lost. I use one of the thin belt sanders to sand the rust out. Put a large light on it and inspect from 5cm close to check if you see any brown specs. Remove any spec that you identify. If you're lucky you will have 0.6mm left of the 0.8 mm sheet thickness. Thats enough to paint over.
If you sand through the rust, then you haven't lost any good steel, it was rust and must be replaced anyway.

I also use a carbide cutting tool on an airspindle to form welds (and steel). Easy to use for small details as these. Take care of the chips flying off; the're raisor sharp.

Mind you that when you weld, there is also a backside to treat. After welding i always treat the backside. Paint or wax, but at least do something or it will be back in 10 uears rusted from behind.

I had holes in the rear window frame, not unlike your pics, but a real hole. First thing i did is drill through (~6mm) , including the opposite sheet forming the channel/cavity. Then weld and grind flat. With that second hole i could spray paint inside the cavity that forms the window frame, to the backside of the plug welded hole.
Click to expand...
This is a great example of the value of this site. A great resource of people who aren’t selling anything, that just want to share what they’ve learned.
 
e9coupeMA said:
You guys all are great. Thank you. can you voice any opinions as to what you think might be going on here? I almost feel with the pimple like paint that it's a paint failure issue but the little rust spot make me think it maybe something coming up from below. Thoughts?
Click to expand...
A couple things come to mind. First, the paint should never come off like that, which is a sign of incorrect prep or the primer and top coat not bonding properly. You might be right about the little rust spot but it might also be a nick in the paint that rusted over time giving the paint a chance to separate. Neither spot looks bad but matching that paint might be tricky.
 
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