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This cannot be good... I'm in the midwest, and my 2017 forester I bought last summer was parked outside for the past winter. I don't know how much corrosion there was before I owned it because I either never thought to check or didn't notice if I did... What should I do now? These photos were taken tonight, and no, I cannot sleep.
tempImagejhJUsA.jpg tempImageUA40Vg.jpg tempImageaHkphf.jpg tempImagedukRcD.jpg
 

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2015 Forester Premium CVT
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There is nothing you can really do. Some will suggest that you use Krown or Fluid film but according to my mechanic, if you do that, you could end up making things worse (Some will strongly disagree with that.). I think this is just a fact of life for us in the salt country.

I have started washing undercarriage regularly during winter but thats about it.
 

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2001 Forester S, 4EAT
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That's pretty much par for the course. My 2001 Forester S, looks just like that and it's been that what now for as long as I can remember since buying it new.
 

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2021 Forester Base Automatic
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195 Posts
Spray the underside with Corrosion Stop by PB blaster. This will delay corrosion and if you ever have to loosen any bolts it will help a lot. If you can lightly brush off any loose rust first it will help. Also wash the underside at least every spring. You will always have rust if you live in the salt belt. Subarus don't rust too badly. I've seen many brand new Jeep Wranglers that have rust on the dealers lot, my 2016 did. CORROSION STOP – Blastercorp
 

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2017 Forester 2.5 Premium, Black
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I have had good luck with POR15 (a black anti rust paint). Used by classic car resto shops. Can be had on EBAY or at Eastwood a auto body tool dealer.
 

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MY05 Forester 2.5 XT 5MT
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Hi and welcome to the forum.

For a 2017 vehicle, that doesn't look ideal being so new.

The good news is at this point, it appears it can be sorted without replacing parts, short of a few bolts perhaps. How long you have until it becomes more serious and a safety issue, I wouldn't like to say.

I'm surprised by the previous comments saying it is nothing to worry about...... If it was a 1998 vehicle, I'd be inclined to agree but something so new with a lot of value potentially still, I would be looking to sort at least the more major parts for a prolonged life, especially if there is a long term finance arrangement in place etc.

At this point, I would be wondering if you have your own tools and a covered parking space/garage and do you have the time to spend on this and do you have a second vehicle to use while sorting the Forester out?

The transmission casing could probably be sorted out in situ but I would be tempted to remove the cross member, press out the bushings and get it sand/soda blasted, zinc primed, then powder coated. Then press the bushings back in and bolt it back onto the car.

Have a look at these threads, paying attention to @Lockheed 's input as he really knows what he is doing with rust.
 

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2018 X3 M40i / 2016 X3 xDrive35i
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There is nothing you can really do. Some will suggest that you use Krown or Fluid film but according to my mechanic, if you do that, you could end up making things worse (Some will strongly disagree with that.). I think this is just a fact of life for us in the salt country.

I have started washing undercarriage regularly during winter but thats about it.
I've been using fluid film and will STRONGLY disagree with the claim it would make it worse. Absolutely 100% not.
 

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MY05 Forester 2.5 XT 5MT
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+1 Sealing the rust does not solve the problem - It simply hides it. You need to stop and treat the rust first, then you can add your sealants afterwards to prevent rusting in the future. It should not be used on "active" rust as you can indeed just make the problem worse.
 

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2008 LL Bean (4EAT)
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This cannot be good... I'm in the midwest, and my 2017 forester I bought last summer was parked outside for the past winter. I don't know how much corrosion there was before I owned it because I either never thought to check or didn't notice if I did... What should I do now? These photos were taken tonight, and no, I cannot sleep...
It looks normal for a car that was driven every day in salty winters.

My 2008 still looks new underneath, with all the metal still black and the bolts bright silver. It has 70,000 miles, and has been all over the country from Maine to Washington and Canada to Florida. In winters, my city of Louisville brings barges of salt up the Ohio River and covers the roads with it. However, I am able to avoid driving that car until the roads are rain-washed, except for a few times a year, after which I do wash the bottom.

I use a bottom washer made per this forum post:
Picture of it:
554042

A couple of times a year, when I wash the car, I use a hand mitt to reach up and clean the front and rear wheel wells and struts. For the front, I leave the engine running and turn the wheels to better reach the struts and control arms on each side.
 

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2004 forester sti
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2,540 Posts
Im surprised at how much surface rust there is but as far as i can tell its not on the actual monocoque body (no frame)
However its thought provoking because japan knows full well about rust issues and has done since the late 1970s (anyone heard of Datsun now Nissan that French company)
I digress, and heres another thought.
Ive been involved in many restoration projects and have always been impressed that a leaking engine or transmission has always spared and protected the spine of a vehicle while the rest of it goes back to the earth, which leads me on to say a thin penetrating rust inhibiting wax oil such as dinitrol ml cant be used too early....... On any part of the car.(obviously not the brakes)
Having said all that boring stuff that sort of treatment can lead lead to a major ball ache if any actual panel repair needs doing.... Think setting fire to your car with a mig welder.
Im not a fan of using capital letters to enforce a point but you cant rely on manufacturers to keep your car rust free so her goes.
PREEMPTIVE ACTION.
And good luck.
 

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2015 Forester 2.5i Limited CVT
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The OPs rust can be removed and maintained now while its light. Replace any badly rusted fasteners and paint and exhaust clamps and open heat shields.

Exhaust manifolds are sometimes covered with heat shields. Removing the EM and taking off the heat shields may uncover rust.

I realized this when a friend had to replace her exhaust manifold and I had just replaced their gaskets. Didn’t see anything because of the heat shields. So I plan on dropping the EM and taking off the heat shields to inspect.

A lot of Subaru’s don’t have heat shields on their EMs.

Rust is a battle and getting underneath your vehicles should be done frequently. Salt is a big problem. My friends in Maine have seen their Subaru’s just rot away from salted snow.

I wish Subaru would do better about rust proofing the undercarriage. These cars are made for snow trails.
 

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@Lockheed
Using a wire brush on an angle grinder or by hand, take off any heavy or flaking rust. Wash off with soap and water, let dry completely. Use Rustoleum Rust converter in two light coats.

I don’t paint my exhaust system completely. Just the muffler end and hangars where the black rubber donuts go.
Painting the exhaust traps heat and moisture. IMHO.

Use common sense. Mask off areas like around the muffler end and tip. Don’t paint rubber parts or bushings.
 

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It’s the exhaust system that looks bad. The exhaust has moisture inside and and the salt/snow outside. Hose off when cold then drive to dry off. It’s true that it is light rust, but can turn into heavy rust as each Winter passes.

Are there car washes that spray the undercarriage?
 

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2012 SH Manual Diesel
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I cannot sleep.
Rest easy, as it may not be as bad as it looks.

Most importantly, you want to inspect the underbody of the car, panels, any drain holes (as they clog up), and areas that hide and hold moisture and dirt (mud flaps, wheel arches, behind bumper bars). It’s the thin panels, and the parts that can’t be unbolted and easily replaced, that are the most concern. But in saying that a lot of stuff can be fixed (and done well, if you find the right person).

The diff and driveshaft are very very solid, so worry less about those for the moment. The diff could probably rust for years, and not be too much of a problem. However, I guess it’s possible for the balance of the tail-shaft to be effected; if the rusting is severe and left for many years. The Exhaust can take a fair beating too, and ultimately can easily be replaced.

Start with the cross member; universal joint; and any rusty part that is touching the body, and rubber bushing, seal, or bearing. A rusty part can easily cause rust to occur in an adjacent component, due to the electrical potential of the chemical process (corrosion is a redox reaction, much like in a battery).

Then tackle the Exhaust, starting at the Engine end; as any additional electrical potential (from the rusting exhaust), could possibly add to, or spark off a stray current, leading to corrosion in the cooling system, or engine parts. NB: heat also catalyses chemical reactions. Also consider the theory behind sacrificial anodes, and electronic rust protection devices, and you’ll see where i’m going with all that.

Pay particular attention to nuts and bolts, and components that move; as these have likely already compromised their protective coating (during assembly, and road use, respectively).

Remove all dirt that builds up on the car. As dirt (even in non-salted areas), has an element of salts in it. And its the salts that provide the electrical potential, to accelerate the oxidation process. Dirt, even though it is dry, still contains microscopic moisture.

First of all, stop the rusting process; as this will ease your mind. Clean and degrease underneath the car, and any parts to be treated. Use a product called ‘Fertan’, made by Chemtech. It’s expensive; commonly sold in the Marine industry, and boating shops (for good reason; “it works”); however, a little goes a long way.

You can paint it on, with a small brush, so you only use what you need. The brush can be used to agitate the surface. As the product works, further agitation can be done to help the product penetrate. If and when it dries, you can dip the paint brush in clean fresh water, and wipe over the treated surface, to reactivate the rust conversion process.

The good thing is, you can paint it on, and let it dry; not only will it stop the rusting process; it will convert the rusted metal; and also provide protection for a specified amount of time (i.e. depends on how exposed the part is. Could be weeks, could be months). Simply reapply at intervals to retain rust protection. Alternatively, the Fertan can be painted over, once all the rust has been converted (see product details). Once, you’ve coated all the rusty parts; not only will it not look so devastating; but, you’ve just bought yourself plenty of time to deal with the issue. You can then go about tackling your move longterm rust prevention plan.

Evapo-rust and Rust Remover Gel, are also very good products. Evapo-rust is good for soaking items.

Other techniques for corrosion protection is metal bluing (search YouTube), used in tool manufacture, and Gun smithing. Can be as simple (and cheap), as ‘heating and quenching’ (in oil); or wiping on a bluing compound, which etches into the metal (probably too expensive for under the car, but thought i’d mention it for other uses). Although, nuts and bolts that have lost their protection (zinc plating, oxidation etc), could be a candidate for metal bluing.

If painting, remove or convert all traces of rust pedantically (otherwise it may fester underneath the paint). Then use a rust inhibitor primer, then a rust proofing ‘enamel’ paint. Be pedantic on the paint process, so you get the most durable coating possible (as stone chips, will just allow the corrosion to start again).

If you’re confident that all the rust is treated, then a film coating or sealant may help. It would always be a good idea to clean off any dirt and salt as soon as practicable, as well as monitoring the condition. Films and sealants can be an issue; if they seal dirt, moisture, and rust in; or if they plug up drainage holes. However, if you drive on rough roads, with rocks, debris, and salt etc.; it could appear that the films/sealants are ineffective (but its also possible, that the rust may have been far worse, without them). It’s something you have to discern for yourself (based on the conditions you live in).

Inspect drainage holes in doors; rear compartment (underneath foam trays), and down the rear side panel (near cabin air vents); for Moonroof (if fitted); and plastic combing underneath windscreen wipers.

Inspect bolts and mounts for the radiator, tow bar, and brake lines; also screws for rear bumper (plastic inserts), gas struts on tailgate, and rubber bracket/bumper on body (for rear tailgate); as moisture can run up threads by capillary action. Another potential rust spot, can be around the plastic inserts (that push into the panels), which hold the rear tail light assemblies; and the bracket that the rear bumper sits on (have to take bumper off to see it).

There are three sure things in life; death; taxes; and rust. And in the words of Neil Young “rust never sleeps”....
 

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Rust (iron oxide) is the result of iron chemically combining with oxygen when exposed to air and or water.
Salt does not cause rust; it has no oxygen.
However, salt attracts and holds water (and the oxygen within).
When salt sits on your shiny metal part, it attracts the moisure that causes rust.
Do not ever buy a late model salvage title that been driven into the ocean: you will never be able to entire remove the salt and everything will rust from the inside.

Salted roads also contain some grit, gravel, crusher fines, whatever, that delivers a double whammy to undercarriages: the salt & water causes rust, and the grit blasts off the rust and exposes fresh shiny steel for salt to settle on.

If you do not remove the salt, it will continue to pull moisture out of the air. This is a much bigger problem if you live in high humidity. The salt concentrates oxygen on the iron of your steel part and will create rust forever, or at least as long as there is a steady supply of fresh iron.

To stop rust, remove the salt, either at the DIY car wash, or:

My 2008 still looks new underneath, with all the metal still black and the bolts bright silver. It has 70,000 miles, and has been all over the country from Maine to Washington and Canada to Florida. In winters, my city of Louisville brings barges of salt up the Ohio River and covers the roads with it. However, I am able to avoid driving that car until the roads are rain-washed, except for a few times a year, after which I do wash the bottom.

I use a bottom washer made per this forum post:
Picture of it:
View attachment 554042
A couple of times a year, when I wash the car, I use a hand mitt to reach up and clean the front and rear wheel wells and struts. For the front, I leave the engine running and turn the wheels to better reach the struts and control arms on each side.
 
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