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Discussion Starter · #1 ·
Hi Guys,

After doing some maintenance on my wife's car, I gave it a good look over. After 50k and 5 winters the underside looks pretty good. Only concern I saw were the subframes and front control arms where rust is starting to setup shop (mostly on the weld seams). As a precaution, I just sprayed my wifes car with snot (fluidfilm inside and surfaceshield outside) over the weekend. The rear bumper is a little rusted too, but since that's much easier to replace than a subframe I might just leave it until later.

I attached some pics to compare.

From anyone else's experience, should I keep a lookout in any other areas?

Automotive tire Motor vehicle Bumper Vehicle Automotive exterior
Automotive tire Motor vehicle Wheel Wood Rim
20220910_104610_d.jpg


Motor vehicle Automotive tire Hood Vehicle Bumper
Tire Wheel Land vehicle Vehicle Motor vehicle
20220910_124555fr.jpg
 

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2012 OB , 2017 Impreza
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After 50k and 5 winters the underside looks pretty good. Only concern I saw were the subframes and front control arms where rust is starting to setup shop
Your photos depict about 2 Vermont winters..... unfortunately, the salt (we pay to have spread on the roads) also corrodes our cars (which we also pay for).

There are some parts of the southwest USA where you can drive 20 years before it looks like this. There, you would wear out suspension before rust is a problem.
 

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Discussion Starter · #5 ·
consider chemically converting existing rust before applying a moisture barrier...
People who swear by oil undercoatings said converting wasn't needed. That's a must for rubberized undercoatings or if I wanted to paint over it. It's also mainly surface rust and I just wanted to nip it in the butt sooner than later. I'll compare the 20 or so pictures I took to what it looks like next year. If needed, I'll buy some Rust Kutter.
 

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Discussion Starter · #7 ·
My approach is fluidfilm inside the frame rails and anywhere else I can't reach, and POR-15 the rest.
You've had good experience with the POR-15? I've heard mixed reviews, but that could be poor prep or application.

Either way it seems like a hybrid solution is the way to go, unless you have so much paint you could dip parts into it. :unsure:
 

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You've had good experience with the POR-15? I've heard mixed reviews, but that could be poor prep or application.

Either way it seems like a hybrid solution is the way to go, unless you have so much paint you could dip parts into it. :unsure:
Yes, as long as you degrease and wire brush first, it works incredibly well. I got the small 4oz can that they sell on Amazon and it was more than enough to cover both subframes. I used a cheap foam brush to apply it. It has been several years and there's no sign of any degradation. With that said, I do think the bigger benefit for longevity and preventing rust perforation is to FluidFilm the inside of the subframes and all the nooks and crannies. It's just a lot messier than a nice clean POR-15 finish.
 

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2019 Outback Wagon 2.5i limited
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Yes, as long as you degrease and wire brush first, it works incredibly well. I got the small 4oz can that they sell on Amazon and it was more than enough to cover both subframes. I used a cheap foam brush to apply it. It has been several years and there's no sign of any degradation.
To be clear, you just did the subframe, not the whole undercarriage? My old ‘08 did well with just the electronic rust control module (I forget the brand) that was offered by the dealer at that time. I transferred it to my ‘19, I’m just not sure if the factory rust inhibitor was better on the Gen 3 or if it was the ERM that was in stalled. I guess time will tell if my Gen 5 staves off the rust.


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To be clear, you just did the subframe, not the whole undercarriage? My old ‘08 did well with just the electronic rust control module (I forget the brand) that was offered by the dealer at that time. I transferred it to my ‘19, I’m just not sure if the factory rust inhibitor was better on the Gen 3 or if it was the ERM that was in stalled. I guess time will tell if my Gen 5 staves off the rust.


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I did the whole undercarriage, but the front and rear subframe got extra treatment as those are the bits that I have no desire to ever want to replace, and also there have been reports of subframe failure due to rust on Gen 4's which have similar subframes as Gen 5's. I've always been skeptical of electric rust control.
 

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I don’t blame you for being skeptical, I was (am kind of still am). The brand they used had a good track record of being used in the salt mines and such. My ‘08 was really rust free after 170k miles in 12 years in the rust belt of Ohio. Just a little surface rust in the suspension components. I’m pretty sure they went under for some reason. The brand I have on my F150 doesn’t seem to be working as well, do I still use FF.


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Discussion Starter · #12 ·
To be clear, you just did the subframe, not the whole undercarriage? My old ‘08 did well with just the electronic rust control module (I forget the brand) that was offered by the dealer at that time. I transferred it to my ‘19, I’m just not sure if the factory rust inhibitor was better on the Gen 3 or if it was the ERM that was in stalled. I guess time will tell if my Gen 5 staves off the rust.


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That's correct, just the subframe at this time and not the whole undercarriage. Agan only the subframe and front control arms looked worse than everything else. Center of the car looks new. Crumple zones in the front and back look great. I'll probably spray the rear bumper soon since that was iffy.

I'm not sure what to make on those electronic rust inhibitors. Reviews are mixed and some people say it's because of the newer unibody construction. Other said they help the body, but not the chassis.

I kind of wish Project Farm or Repair Geek could get to the bottom of this debate for us.
 

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When updating my suspension, I noticed the rear subframe had a bit of surface rust, particularly around the welds. I ordered some rust encapsulater from Eastwood to spray on. Then, I'll top coat it with 3M undercoating and spray some fluid film in the hard to reach areas.
 

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2010 Outback 3.6R 2014 Legacy 2.5i
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1. that's normal
2. you can use rust wire brush and rust converter to clean it up
3. use etching primer
4. paint with black paint

profit.

here is a 13.5 year old outback for comparison
Automotive tire Motor vehicle Rim Automotive exterior Automotive design
Automotive tire Automotive exhaust Motor vehicle Rim Automotive lighting
Tire Automotive tire Motor vehicle Vehicle Hood
 

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What your showing is not anything to be concerned about. I'm from New England and live in UpState NY. This is exactly how my 17 OB Limited looks with 120k and my 15 F150. Surface rust.
IMO at the current rate of rust 15 years +/- reasonable to assume.

I chased my tail researching this topic. If I lived in VT, NH, ME I'd have a pro proof it but what your showing is actually looking good.

Biggest? Is how long do you plan on keeping it.
 
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