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Discussion Starter #1
Not sure if this is the right place to post this but...

I recently purchased an 09 MS3, for some reason it had a receiver hitch bolted to the bumper. In order to remove the hitch I had to pull the rear bumper cover. Throughout the process I noticed some rust here and there. Such as; the bumper itself, the floor of the inside of the trunk area, the body of the car where the bumper bolts to it, the seam where the hatch weather seal is installed.

the bumper itself I’ll probably take to my local powder coater and have them sand blast it for me. I don’t know what i should do about the rest of the rust. I despise rust so this is bothering me more than it probably should. I’ve heard of the rust specific paint ‘POR15’ but I’ve never used it.

Any and all advice on how to fix this will be greatly appreciated

Thanks!
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Kudos for wanting to be proactive about it; all you've pictured looks superficial enough to me that I think you could significantly stall its progression. I'll give you some food for thought that you can chew along with advice from other folks:
  • for the hatch gasket rust, I'd remove the gasket, then lightly sand the rust by hand. Clean with isopropyl alcohol to remove sanding residue. You could then either paint on POR-15 in the "footprint" of the gasket (caution, it'll stain clothes and skin if you're not careful -- or even if you are -- wear safety glasses and go slow; you can get it in small pint cans, and that's what I typically use so as to not worry about overspray); taping things off and using Rustoleum is also an option. Give it time to cure. You can reapply the gasket in a number of ways -- a bead of RTV silicone as water-sealing adhesive; brushed on silicone paste to the lip, then press the gasket on; wax the lip and "footprint", hand buff, then apply the gasket... You may have realized that the compression/release of the gasket causes minute friction on the footprint, eventually letting the blocked moisture past the paint barrier.
  • For the bumper mounts, I'd wire-wheel with a power drill, then you could treat with POR-15/Rustoleum like for the hatch rim. For a hidden part like that, I would go with several coats of Rustoleum "rust reformer", with the last coat being glossy to minimize moisture sitting on textured coatings like flat/satin. I have used POR-15 in that area, and on the bumper bar, but, in hindsight, POR-15 can be prone to flaking if the surface prep wasn't excellent (they make complementary products like "Metal Prep" and degreaser, but soon you're building a chemical stockpile). In my experience "pretty good" rust treatment buys you a great deal of time, often outlasting your ownership; if "perfect" leaves me holding more bottles of chemical than I care to, "pretty good" is good enough. Tape off the bumper threaded studs so they don't get gummed with paint, and I might use a dab of anti-seize on them during reassembly, but ensure they're sufficiently torqued.
  • that "side saddle" rust (the pocket with the plastic dust/water body plug), it's obviously tougher. I'd probably hand-sand as best I could, wipe with isopropyl alcohol, then hand paint some POR-15 in there (or spray Rustoleum onto a disposable sponge brush, just to get some coverage on the sanded metal. (You can spritz spray paint directly in there, but then you're going to get more fumes lingering in the car for a while.) Once the light coating's cured, I'd try to wax in there, or spray Fluid Film as a moisture barrier. I think the nature of that pocket lends itself to surface corrosion, but a barrier like wax or Fluid Film will keep the moisture/condensation for eating at the metal in the way it's been.
  • Any other surface rust can be addressed with principles above.
 

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Discussion Starter #3 (Edited)
Kudos for wanting to be proactive about it; all you've pictured looks superficial enough to me that I think you could significantly stall its progression. I'll give you some food for thought that you can chew along with advice from other folks:
  • for the hatch gasket rust, I'd remove the gasket, then lightly sand the rust by hand. Clean with isopropyl alcohol to remove sanding residue. You could then either paint on POR-15 in the "footprint" of the gasket (caution, it'll stain clothes and skin if you're not careful -- or even if you are -- wear safety glasses and go slow; you can get it in small pint cans, and that's what I typically use so as to not worry about overspray); taping things off and using Rustoleum is also an option. Give it time to cure. You can reapply the gasket in a number of ways -- a bead of RTV silicone as water-sealing adhesive; brushed on silicone paste to the lip, then press the gasket on; wax the lip and "footprint", hand buff, then apply the gasket... You may have realized that the compression/release of the gasket causes minute friction on the footprint, eventually letting the blocked moisture past the paint barrier.
  • For the bumper mounts, I'd wire-wheel with a power drill, then you could treat with POR-15/Rustoleum like for the hatch rim. For a hidden part like that, I would go with several coats of Rustoleum "rust reformer", with the last coat being glossy to minimize moisture sitting on textured coatings like flat/satin. I have used POR-15 in that area, and on the bumper bar, but, in hindsight, POR-15 can be prone to flaking if the surface prep wasn't excellent (they make complementary products like "Metal Prep" and degreaser, but soon you're building a chemical stockpile). In my experience "pretty good" rust treatment buys you a great deal of time, often outlasting your ownership; if "perfect" leaves me holding more bottles of chemical than I care to, "pretty good" is good enough. Tape off the bumper threaded studs so they don't get gummed with paint, and I might use a dab of anti-seize on them during reassembly, but ensure they're sufficiently torqued.
  • that "side saddle" rust (the pocket with the plastic dust/water body plug), it's obviously tougher. I'd probably hand-sand as best I could, wipe with isopropyl alcohol, then hand paint some POR-15 in there (or spray Rustoleum onto a disposable sponge brush, just to get some coverage on the sanded metal. (You can spritz spray paint directly in there, but then you're going to get more fumes lingering in the car for a while.) Once the light coating's cured, I'd try to wax in there, or spray Fluid Film as a moisture barrier. I think the nature of that pocket lends itself to surface corrosion, but a barrier like wax or Fluid Film will keep the moisture/condensation for eating at the metal in the way it's been.
  • Any other surface rust can be addressed with principles above.
Thank you so much for taking the time to right this out. I really appreciate it. Like you said about the POR15, I have read that if it is not prepared correctly that it will flake off and peel up. I’ve also been reading about a rustoleum product that is similar in effectiveness (I can’t recall the name of it, I’ll have to go back and look it up).

whichever product I do decide to use I will prefer it in brush on form. As I really don’t want to make a mistake and get overspray where I don’t want it.

I won’t need to topcoat it correct? Since it’ll be underneath trim it will never see the sun

EDIT: I have heard of this product, corroseal. Goes on like paint, converts rust to black. Then can be painted over. If I use that, could I paint over it with something like a rustoleum enamel paint like this?

https://www.lowes.com/pd/Rust-Oleum-128-fl-oz-Interior-Exterior-Gloss-White-Paint/3067159
 

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Correct -- I believe TopCoat is used to add UV-resistance to POR-15; I didn't top coat it when I used it on my bumper bar surfaces, just applied it liberally. I also used it in my very rusty spare tire well (previous owner rear-ended, with inadequate sealing of hatch thereafter), after wire-wheeling and using their Metal Prep product. I noticed some rust coming through a couple years later.

I haven't used Corroseal before, but it looks straightforward (maybe even preferable to POR-15?), and the product video on their site suggests there shouldn't be an issue topcoating with that Rustoleum you linked. (I'd still recommend eye, skin, and respiratory precautions for Corroseal; their video portrays it as remarkably safe, but the MSDS speaks to toxicities and irritations to be cautious about.) FWIW, I wouldn't be afraid of using a rattle can -- you can effectively limit overspray with cut-open trash bags and painter's tape. However, if you don't want to deal with masking things off, brush-on isn't a bad way to go for hidden surfaces.
 

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Discussion Starter #5
Correct -- I believe TopCoat is used to add UV-resistance to POR-15; I didn't top coat it when I used it on my bumper bar surfaces, just applied it liberally. I also used it in my very rusty spare tire well (previous owner rear-ended, with inadequate sealing of hatch thereafter), after wire-wheeling and using their Metal Prep product. I noticed some rust coming through a couple years later.

I haven't used Corroseal before, but it looks straightforward (maybe even preferable to POR-15?), and the product video on their site suggests there shouldn't be an issue topcoating with that Rustoleum you linked. (I'd still recommend eye, skin, and respiratory precautions for Corroseal; their video portrays it as remarkably safe, but the MSDS speaks to toxicities and irritations to be cautious about.) FWIW, I wouldn't be afraid of using a rattle can -- you can effectively limit overspray with cut-open trash bags and painter's tape. However, if you don't want to deal with masking things off, brush-on isn't a bad way to go for hidden surfaces.
Sweet. Are there common leak points around the rear hatch/back of these cars? I noticed moisture in the spare tire well under the spare tire foam.
 

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Sweet. Are there common leak points around the rear hatch/back of these cars? I noticed moisture in the spare tire well under the spare tire foam.
Once you sponge-up and dry the tire well water, you might shake some chalk dust or a light coating of baking soda -- something that could help identify the source of a leak. I'm not sure whether there are common leak points; my hatch gasket/weatherstripping was completely wrong (so I replaced it from a salvage yard), and I thought there might be small separations at the body seams below each front-to-rear roof gutter when it turns into the hatch border (so I cleaned those seams and put some POR-15 then RTV silicone over them).
 

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Discussion Starter #7
Once you sponge-up and dry the tire well water, you might shake some chalk dust or a light coating of baking soda -- something that could help identify the source of a leak. I'm not sure whether there are common leak points; my hatch gasket/weatherstripping was completely wrong (so I replaced it from a salvage yard), and I thought there might be small separations at the body seams below each front-to-rear roof gutter when it turns into the hatch border (so I cleaned those seams and put some POR-15 then RTV silicone over them).
I have noticed some rtv along my front to rear roof gutters as well. Is there an area under the black strip that could leak water into the vehicle?
 

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The only thing that's going to leak that's actually under the gutter trim is the hidden roof rack fixed-points, if they've been bent by rack overload. You'd probably see staining on the headliner if that were the case.

I'm talking about the seam that runs down from the gutter, into the hatch recess. In this salvage yard photo, you can see some scant rust along the line:
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Since mine had been previously rear-ended, I wondered if there were micro-perforations letting in water. Not highly likely, since I was getting a lot of water (mainly from the gasket/weatherstripping), but I treated and sealed the seam as preventative maintenance.
 

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Discussion Starter #9
The only thing that's going to leak that's actually under the gutter trim is the hidden roof rack fixed-points, if they've been bent by rack overload. You'd probably see staining on the headliner if that were the case.

I'm talking about the seam that runs down from the gutter, into the hatch recess. In this salvage yard photo, you can see some scant rust along the line:
View attachment 105914
Since mine had been previously rear-ended, I wondered if there were micro-perforations letting in water. Not highly likely, since I was getting a lot of water (mainly from the gasket/weatherstripping), but I treated and sealed the seam as preventative maintenance.
Thanks for the pic, gives me a clear idea of that area you were talking about
 

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Kudos for wanting to be proactive about it; all you've pictured looks superficial enough to me that I think you could significantly stall its progression. I'll give you some food for thought that you can chew along with advice from other folks:
  • for the hatch gasket rust, I'd remove the gasket, then lightly sand the rust by hand. Clean with isopropyl alcohol to remove sanding residue. You could then either paint on POR-15 in the "footprint" of the gasket (caution, it'll stain clothes and skin if you're not careful -- or even if you are -- wear safety glasses and go slow; you can get it in small pint cans, and that's what I typically use so as to not worry about overspray); taping things off and using Rustoleum is also an option. Give it time to cure. You can reapply the gasket in a number of ways -- a bead of RTV silicone as water-sealing adhesive; brushed on silicone paste to the lip, then press the gasket on; wax the lip and "footprint", hand buff, then apply the gasket... You may have realized that the compression/release of the gasket causes minute friction on the footprint, eventually letting the blocked moisture past the paint barrier.
  • For the bumper mounts, I'd wire-wheel with a power drill, then you could treat with POR-15/Rustoleum like for the hatch rim. For a hidden part like that, I would go with several coats of Rustoleum "rust reformer", with the last coat being glossy to minimize moisture sitting on textured coatings like flat/satin. I have used POR-15 in that area, and on the bumper bar, but, in hindsight, POR-15 can be prone to flaking if the surface prep wasn't excellent (they make complementary products like "Metal Prep" and degreaser, but soon you're building a chemical stockpile). In my experience "pretty good" rust treatment buys you a great deal of time, often outlasting your ownership; if "perfect" leaves me holding more bottles of chemical than I care to, "pretty good" is good enough. Tape off the bumper threaded studs so they don't get gummed with paint, and I might use a dab of anti-seize on them during reassembly, but ensure they're sufficiently torqued.
  • that "side saddle" rust (the pocket with the plastic dust/water body plug), it's obviously tougher. I'd probably hand-sand as best I could, wipe with isopropyl alcohol, then hand paint some POR-15 in there (or spray Rustoleum onto a disposable sponge brush, just to get some coverage on the sanded metal. (You can spritz spray paint directly in there, but then you're going to get more fumes lingering in the car for a while.) Once the light coating's cured, I'd try to wax in there, or spray Fluid Film as a moisture barrier. I think the nature of that pocket lends itself to surface corrosion, but a barrier like wax or Fluid Film will keep the moisture/condensation for eating at the metal in the way it's been.
  • Any other surface rust can be addressed with principles above.
In regards to using isopropyl alcohol to clean metal before applying a coating/paint. Won’t the alcohol leave a residue behind? Will it remove existing paint?
 

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In regards to using isopropyl alcohol to clean metal before applying a coating/paint. Won’t the alcohol leave a residue behind? Will it remove existing paint?
It's just a quick-and-dirty way to get most loose contaminants and oils off for painting. I've used isopropyl alcohol and a lint-free cloth for years with satisfactory results. No, it's not a perfect method, and yes, it'll erode existing clear coat or paint if you scrub and are careless with focusing your bodywork. To more perfectly remove residue, many paint prep degreasers are available. If you're pursuing professional results, you'll want to do prep work indoors, filtered air, anti-static, well-exhausted/ventilated -- or as close to those parameters as you can get.
 

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Discussion Starter #12
It's just a quick-and-dirty way to get most loose contaminants and oils off for painting. I've used isopropyl alcohol and a lint-free cloth for years with satisfactory results. No, it's not a perfect method, and yes, it'll erode existing clear coat or paint if you scrub and are careless with focusing your bodywork. To more perfectly remove residue, many paint prep degreasers are available. If you're pursuing professional results, you'll want to do prep work indoors, filtered air, anti-static, well-exhausted/ventilated -- or as close to those parameters as you can get.
Was just worried about wether or not it left a film. Didn’t want the rust converter to not do it’s job, then cause the paint not to stick etc. I can get a gallon of 70% isopropyl alcohol for about $25 at the local tractor supply
 

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I can get a gallon of 70% isopropyl alcohol for about $25 at the local tractor supply
Whoa! Pump the brakes: unless you have a lot of things you need to do with that isopropyl, an inexpensive 32oz bottle (91% or 70%) can be had at most grocery or drug stores. Even that would be more than enough for repeated wiping down of everything you pictured, IMO.

Edit: also, to assuage your worries about residue and adhesion, be sure to practice your approach on a small part of your issues, so you can see if the result is satisfactory.
 

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Whoa! Pump the brakes: unless you have a lot of things you need to do with that isopropyl, an inexpensive 32oz bottle (91% or 70%) can be had at most grocery or drug stores. Even that would be more than enough for repeated wiping down of everything you pictured, IMO.

Edit: also, to assuage your worries about residue and adhesion, be sure to practice your approach on a small part of your issues, so you can see if the result is satisfactory.
Lol yeah. A gallon is a bit much. I had to order the corroseal on Amazon. I called the company to confirm the paint I was going to use would work with their product. They said it will be fine.

I scrubbed the bumper brace down with simple green and rinsed it today. Looks like I’ll have to spray an aerosol rust converter within it, as there is rust inside that I can’t reach with a brush
 

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I have been using Krown Krown Rust Control every year i have had the 2012 and have not run into any rust issues ( i drive on salted winter roads)

Where surface areas or missed hidden rust spot do show i use their product in can Rust Protection & Lubricant
I spray and walk away ..neutralizes the rust . It seeps into it and into unseen areas too .

Painting over rusted areas ... you need to really get to down to bare metal and spray 4-8 coats of paint . Thats with the rust you see

My Hood is my issue ... mainly paint chips from rocks starting to create surface rust specs ...
Taking the hood off this summer ...
 

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I have been using Krown Krown Rust Control every year i have had the 2012 and have not run into any rust issues ( i drive on salted winter roads)

Where surface areas or missed hidden rust spot do show i use their product in can Rust Protection & Lubricant
I spray and walk away ..neutralizes the rust . It seeps into it and into unseen areas too .

Painting over rusted areas ... you need to really get to down to bare metal and spray 4-8 coats of paint . Thats with the rust you see

My Hood is my issue ... mainly paint chips from rocks starting to create surface rust specs ...
Taking the hood off this summer ...
My hood has quite a few rock chips as well, as does the rest of my car. Some of them are now rusted. Hopefully they can be touched up and blended, I do not want to paint the entire car.
 

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My hood has quite a few rock chips as well, as does the rest of my car. Some of them are now rusted. Hopefully they can be touched up and blended, I do not want to paint the entire car.
Yup same issue here ...rest of body is good.. hood and front bumper is a rock chip mess ...
Or other option im thinking of vinyl wrap the hood black (my car is white) , continuing width of front hood down the bumper. maybe with an burnt orange color stripe (same color as the calipers) that starts solid and slowly fades 3/4 up the hood (maybe 2 stripes) and same orange color on the outside of mirrors.
This orange cailper color ---> NEO Motorsport Brakes & Suspensions
 

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Yup same issue here ...rest of body is good.. hood and front bumper is a rock chip mess ...
Or other option im thinking of vinyl wrap the hood black (my car is white) , continuing width of front hood down the bumper. maybe with an burnt orange color stripe (same color as the calipers) that starts solid and slowly fades 3/4 up the hood (maybe 2 stripes) and same orange color on the outside of mirrors.
This orange cailper color ---> NEO Motorsport Brakes & Suspensions
That would look good. I hear a good quality wrap can last a while with proper maintenance.
I’d like to get the Gen 1 hood with a scoop.
But that’s $1000 I’d much rather spend on HPFP internals, access port, etc.
 

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That would look good. I hear a good quality wrap can last a while with proper maintenance.
I’d like to get the Gen 1 hood with a scoop.
But that’s $1000 I’d much rather spend on HPFP internals, access port, etc.
Im in the process of doing the internals on the 2.0L
 
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Discussion Starter #20 (Edited)
Wire wheeled all the loose rust off of the bumper today. Washed it with soapy water and let it dry. Then hit it with 2 cans of rustoleum rust reformer. Gonna let it cure overnight before I hit it with some rustoleum industrial enamel
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