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Discussion Starter · #1 · (Edited)
Has anyone in the rust belt undercoated their Ascent? We live in WI and plan on keeping our Ascent for as long as it's driving which will include driving it through winter and all the salt that comes with them.
I didn't take up the dealership on the undercoating they offered, but instead purchased a case of 3M undercoating and went to town on the bottom of the car.
I went through a car wash with a thorough under body spray prior to throwing it on the lift and let it dry before applying.
After going through the 6 cans of undercoating and not even getting the rear end of the car done I gave up and decided to order 2 more cases.
I had to do an oil change/tire rotation in the coming weeks, so I went back at it a couple weeks later. I was happy to see that all of the metal areas that I had previously coated still had the coating on it without any lack of adhesion.

The total of 3 cases (18 cans) was sufficient to cover most of the exposed metal components that are visible under the car without removing more than the under tray under the engine. I coated all 4 wheel wells and applied anti-sieze to the wheel mounting surface and wheel pilot diameter while I had the wheels off to rotate as well.

I think one more case of cans would be good to get the remainder of the spots I missed, so I'll probably save that for the next oil change.
If people are interested I'll post of pictures of how it looks after the months between oil changes.

Here's a link to what I used: https://www.amazon.com/gp/product/B00MJ9FONI/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
3M part number: 08881

If you are going to apply this I highly suggest wearing a respirator. I didn't on the first application and even with the garage door open it was very fumy. The wife came out for about 1/2 hour and had to go inside after feeling a little loopy during the second application.
 

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Have you done it that way on any previous vehicles? I'm curious how it compares to whatever the dealer would've done.
I've only been under my Ascent once on a lift and the first thing I noticed is that practically everything is covered. To me that means there are a lot of areas that water/salt spray will get into that you might not have gotten coated without removing panels. I'll probably forget by then, but update us in about 10 years!
 

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I also undercoated my Ascent myself. Living in the salt belt, I've found this will make your car last a lot longer without rust issues. The factory coating on these vehicles is good, but rust will occur without undercoating. I undercoated my 2010 Forester when I got it and it has zero rust issues to this day.

I used RP-342 "HEAVY" Military-Grade Rust Preventive Spray. I chose this product because it's what the US military uses and anything with a MIL Spec (MIL-PRF-16173, Grade 4 and MIL-C-83933) has been thoroughly vetted for effectiveness. You can buy it in 1 to 12 can cases. You will need at least a 12 pack case to do the Ascent. This will cost around $124.

It was fairly easy to do but you definitely need a respirator and a disposable TYVEK suit. The Ascent is easy to climb under especially if you have a creeper. Using an LED headlamp also makes the job a lot easier. It's best to undercoat the vehicle when it's new, but waiting a year or so won't hurt.

I also recommend painting the brake calipers. They will rust for sure within a few years and look terrible. Use high temp epoxy paint of any color you choose. The results will look great and the calipers will function a lot better over the years without rust causing issues.




These are jobs for hardcore DIY'ers and not for the faint-hearted. Neither is hard, but both are messy and if you don't like to get your hands dirty they're not for you.
 

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Discussion Starter · #5 ·
Have you done it that way on any previous vehicles? I'm curious how it compares to whatever the dealer would've done.
I've only been under my Ascent once on a lift and the first thing I noticed is that practically everything is covered. To me that means there are a lot of areas that water/salt spray will get into that you might not have gotten coated without removing panels. I'll probably forget by then, but update us in about 10 years!
I can't talk to what the dealer does because I've never purchased it or seen someone purchase it.
Based on previous experience with other Subaru's I've owned I see the worst corrosion on:
- Fasteners that are zinc plated, but no other rust preventative feature
- Flat surfaces where water/salt can pool
- Welded components (even after they're painted)
- Painted assemblies that are not on the body during paint (differential, driveshaft, sub frames, etc)

I have never undercoated a new car myself, but I've talked to many other people who have. The hardest thing is definitely getting it up in all of the areas that are hard to reach. Once you think you've hit every area you can go back 2 minutes later and it's like you were never even coating that area because you find another area that's bare. I plan on using some fogging oil to get inside the frame rails and other areas that are enclosed and cannot be sprayed. Either way I can't see this causing any harm or making the corrosion worse. If anything I wasted a few hundred dollars and some time in the garage. :dunno:
 

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Discussion Starter · #6 ·
Did you guys clean the undercarriage pretty thoroughly before applying?
The only cleaning I did was go through a car wash with an under body spray. With that said the car was fairly clean. The Ascent spends 90% of it's time on the road.
 

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I can't talk to what the dealer does because I've never purchased it or seen someone purchase it.
Based on previous experience with other Subaru's I've owned I see the worst corrosion on:
- Fasteners that are zinc plated, but no other rust preventative feature
- Flat surfaces where water/salt can pool
- Welded components (even after they're painted)
- Painted assemblies that are not on the body during paint (differential, driveshaft, sub frames, etc)

I have never undercoated a new car myself, but I've talked to many other people who have. The hardest thing is definitely getting it up in all of the areas that are hard to reach. Once you think you've hit every area you can go back 2 minutes later and it's like you were never even coating that area because you find another area that's bare. I plan on using some fogging oil to get inside the frame rails and other areas that are enclosed and cannot be sprayed. Either way I can't see this causing any harm or making the corrosion worse. If anything I wasted a few hundred dollars and some time in the garage. :dunno:
It will be worth your time if you keep the Ascent for the long haul. When I compare my undercoated 10-year-old Forester to others that were not undercoated, there is a huge difference. The undercarriage looks almost new compared to the rusted mess of the others. And I've had no issues related to rust. However, if you only plan to keep it a few years, then it's not worth the effort.
 

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Did you guys clean the undercarriage pretty thoroughly before applying?
Simply take it to a carwash and clean the undercarriage as best you can. It doesn't need to be perfect, you just need to remove any sand or dirt. Since all Ascents are almost new, rust has not yet done any real damage, so they're still perfectly viable for undercoating.

The wax based undercoatings are better than those that are rubberized or dry hard. They will self heal and never peel off. They form a seal so tough, it will last for over a decade. The only way to remove it is with solvents, it's impervious to water and salt.
 
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