Underbody rust inhibitor.

[BPe90M3]

The underside of my car is in excellent condition for an 8 year old car, however there are a few spot on my subframe that are ever so slightly starting to form rust spores (mostly around the welds on the subframe). I do not drive the car in rain, snow, or the winter seasons, so I want to stop it in its tracks while also covering up the small areas where it has already formed.

I have read a lot about Por-15. Anyone have experience with it? Im definitely not dropping the subframe and really just looking to quickly mitigate what is already there. Is Por-15 as simple as just applying to the areas, or do you need to prep the surface (wire brush/grinder). Or maybe someone can recommend something that I can just spray on and forget about. Any suggestions are much appreciated.

Pictures provided.

[UPSROD]

You should have really bought that UTAH car!!! lol

[BPe90M3]

Originally Posted by UPSROD

You should have really bought that UTAH car!!! lol

That answers my question! Thanks!!

[deansbimmer]

From those shots I'd say your undercarriage is cleaner than half the cars I see in Texas...

POR-15 is not a surface treatment like Armor-All. The prep for its application is the same as it would be for paint or powdercoating. Full disassembly, stripping of old coating (media blast etc), and cleaning/degreasing is the only way to go. It will look ridiculous if you just brush it only onto certain rusty areas.

I've never been a fan of POR-15. I would see it all the time in the hotrod industry. It was a hallmark component of shoddy "restorations". I only ever saw it slathered over old rust. Never done right....

[BPe90M3]

Originally Posted by deansbimmer

From those shots I'd say your undercarriage is cleaner than half the cars I see in Texas...

POR-15 is not a surface treatment like Armor-All. The prep for its application is the same as it would be for paint or powdercoating. Full disassembly, stripping of old coating (media blast etc), and cleaning/degreasing is the only way to go. It will look ridiculous if you just brush it only onto certain rusty areas.

I've never been a fan of POR-15. I would see it all the time in the hotrod industry. It was a hallmark component of shoddy "restorations". I only ever saw it slathered over old rust. Never done right....

Hmm. Im surprised you say that my underside looks cleaner than a lot of cars in texas. I haven't been able to find any pictures online similar to mine, but that may be because you can't zoom in enough.

Do you think there is anything I can spray or apply just to mitigate it at this point? Its really not a big deal and wont get much worse because the car would not see salt, snow, or rain.

[dparm]

Some very light surface rust is a cosmetic issue. I would not waste the time or money to fix that.

[BPe90M3]

Originally Posted by dparm

Some very light surface rust is a cosmetic issue. I would not waste the time or money to fix that.

i really just don't want it to get any worse. But advice taken. Thanks for the comment.

[deansbimmer]

Anything you spray on an undercarriage won't last long, regardless of whether you think it won't see rain or snow. The only sure-fire way to stop rust is to mechanically remove it. Additionally, any product you apply down there will only be a magnet for dirt and dust. Your concern is only cosmetic, it would take another 30 years for the rust to grow enough to cause structural concerns.

[BPe90M3]

Originally Posted by deansbimmer

Anything you spray on an undercarriage won't last long, regardless of whether you think it won't see rain or snow. The only sure-fire way to stop rust is to mechanically remove it. Additionally, any product you apply down there will only be a magnet for dirt and dust. Your concern is only cosmetic, it would take another 30 years for the rust to grow enough to cause structural concerns.

Yes I know its only cosmetic. But I just wanted it cosmetically perfect. Thanks for the comment.

[dparm]

Originally Posted by BPe90M3

Yes I know its only cosmetic. But I just wanted it cosmetically perfect. Thanks for the comment.

If it's not even visible until you get under the car, then who cares?

It's only downhill once a car rolls off the assembly line. Once I learned to accept this, and deal with the minor flaws the car picks up over its life, I found myself enjoying the car even more.

[R3dliner]

I've used this on my past cars exhaust with good results
https://www.amazon.com/Bull-Frog-942...g+rust+remover

[burtonsbs5114]

spray paint it black so you can no longer see it??

[wyatth]

Originally Posted by dparm

If it's not even visible until you get under the car, then who cares?

It's only downhill once a car rolls off the assembly line. Once I learned to accept this, and deal with the minor flaws the car picks up over its life, I found myself enjoying the car even more.

This.

I'm OCD but that underbody is fine and needs nothing.

[blue-mw]

Originally Posted by burtonsbs5114

spray paint it black so you can no longer see it??

I've heard mixed reviews on this. Some say it stops rust, others say it actually expedites it by trapping it under the paint. No experience to condone one over the other, just chiming in to invite additional input.

[IB M]

My advice for an easy, low impact approach.

Clean effected areas lightly with fine wire brush to remove rust.
Purchase basic flat black Rustoleum paint spray can or better yet small non-spray can.
Spray paint into shallow paper bow or cup. Make sure to be far away from car or use a cardboard box so that no overspray travels onto car top side.
Use small paint brush to apply Rustoleum to affected areas. Allow to dry. Apply second coat if needed.
This will slow or stop the rust.
Importantly the painted areas will blend in AND still be easy to identify for future inspection or rework.

This may be overkill but why not if it makes you happy.

[Hagasan41]

Great advice from other members. It’s really nothing to worry about as the surface rust in your photos is normal. But, if you’ve got access to a lift or just want to throw the M up on jack stands this stuff is great.

https://www.amazon.com/Boeshield-Cor.../dp/B07CGVZDJ4

Fluidfilm is another good one but I prefer the Boeshield

[G80indy]

Keep it simple

[BPe90M3]

Originally Posted by 330indy

Keep it simple

But do you just spray this on with no prep?

[shimmy23]

Originally Posted by wyatth

This.

I'm OCD but that underbody is fine and needs nothing.

Agree with this.

In fact, unless you are going to spray the entire damn thing I wouldn't touch it. If I were a potential buyer in the future and noticed random sprays of rust inhibitor on a car, i'd pass on it.

OP, you must sit and stare at your car for hours? constantly looking for flaws?

[BPe90M3]

Originally Posted by shimmy23

Agree with this.

In fact, unless you are going to spray the entire damn thing I wouldn't touch it. If I were a potential buyer in the future and noticed random sprays of rust inhibitor on a car, i'd pass on it.

OP, you must sit and stare at your car for hours? constantly looking for flaws?

Just very observant.

[Helmsman]

Simply love the level of details this forum maintain their cars on! OP, judging from the couple of pictures your car looks nice also on the under side. But hey, everything can be brought to the next level!

[pbonsalb]

I wish my car looked like the OP’s car. My 92k mile 2008 M3 is driven year round in NH and they salt and sand the roads here.

But I’d rather have my car look the way it does and drive it than park it in a garage most of the time. If I lived in the south or west, I could drive the car and not have rust, but that is not an option.