Oxidized stock exhaust (warranty?)

[FiSTY]

I was crawling under my (2019) this weekend and noticed my stock exhaust is oxidized pretty heavily. Only have 16k miles on the car and wash it regularly (as Ohio weather allows). Anyone else experience similar issue? Think the dealership will help?

 

[Jabbit]

Yeah that is normal on any car, dealership probably won't do anything.

 

[M-Sport fan]

409/400 series stainless (which is what our factory system is, as well as many aftermarket ones, like Magnaflow, unless otherwise stated as 304 grade), WILL surface rust/oxidize, as is expected for this grade.

 

[Capri to ST]

409/400 series stainless (which is what our factory system is, as well as many aftermarket ones, like Magnaflow, unless otherwise stated as 304 grade), WILL surface rust/oxidize, as is expected for this grade.

Will exhaust systems made out material like ours generally rust all the way through, or is it generally just cosmetic surface rust?

 

[M-Sport fan]

They would most likely have to be in an actual salt bath in order to rust through/perforate, in order to completely rust through, before the rest of the car falls apart around them.

Which is the reason why OEMs choose the 400/409 option for factory systems nowadays, as a cost effective 'compromise' between very costly 304, and plain old dirt cheap aluminized steel->(which might not make it even 2-3 years before actual perforation, in some 'salt soup winter' areas of this country).

 

[mattkosem]

Sorry for the Necro bump, but I have a 2019 as well and am also in Ohio and my exhaust has rusted all the way through and is leaking by the bend before the rear muffler.

Is this typical? This metal can't be stainless, can it? My Golf R is one year older, has seen double the miles in the same winters, and barely has any rust on it at all....just some patina. This pipe is totally coated in rust that is flaking off everywhere and has at least one hole in it.

The mufflers, ironically, look about online with the 409 stuff on the Golf.

--Matt

 

[Intuit]

Southwest Ohio Valley uses enough road salt that I can stay on the motorcycle for the overwhelming majority of Winter. Pretty much aluminum and plastic, it doesn't rust. I remember a year we had a literal salt dust-bowl on the highways. It's really simply because many people with rain tires and momentum-killing traction control can't pass the streets when the slightest amount of freezing precipitation hits the streets.

The side affect of such an insane level of salt brine is, it keeps the dealerships and mechanics busy.

From prior experiences I can tell you, stay on OEM exhaust as long as possible. Once you go aftermarket, you'll be servicing your exhaust at regular intervals. When my OEM goes, I'll look to buy OEM as replacement. Aluminized steel here lasts about 6 to 12 months and this is what EVERY shop here wants to sell you. No, they don't "warranty" the part or labor against rust. I've also done the 409 and it lasted exactly 18 months before leaking. From appearances 304 via Jegs was on route to fail in about 24-36 months but had to unload the vehicle before actual failure. The problem with the aftermarket crap is the thin-wall. So even high grades fail in relatively short time frame.

The oxidation process is accelerated by moisture, as well as the salt brine. Remove salt and as much as is reasonable, don't allow it to stay wet. Short runs and low speeds will rust your exhaust out from the inside; as the acidic water condensation builds up on the inside and doesn't evaporate.

These marine products have helped a lot...
https://www.amazon.com/gp/product/B0000AXVG9/
https://www.amazon.com/gp/product/B004A7J8FW/
https://www.amazon.com/gp/product/B0064N1FOW/

 

[mattkosem]

No way I'm gonna buy a replacement stock exhaust. I ordered a Thermal R&D to replace it because this car needs to be family friendly.

I'm absolutely stunned that an OEM exhaust could not just look corroded, but RUST THROUGH in 4 years. There's no way this pipe is stainless.

--Matt

 

[Intuit]

Expect aftermarket to be worse.

 

[mattkosem]

🤔 not sure I agree with that. I don't necessarily care that much if it doesn't, and there's nothing I can do about if it that's the case, but I've never seen 304 rust in Ohio winter...let alone rust enough to lose structure. Crack maybe in very high heat applications, sure, but not meaningfully corroded.

Our Golf R's OEM 409 stuff barely has more than a patina on it after 5 winters, and the Milltek 304 stuff on my older Golf just has discoloration on it after over a decade.

Not sure what it's like where you are, but it sounds way worse than where I am.

--Matt

 

[Intuit]

As mentioned prior, I had 304 rust, badly. "Stainless" is not rust-proof.

 

[M-Sport fan]

High grade, true austenitic 304 stainless has to last longer than 2-3 years before perforation, regardless of the gauge, unless it is totally immersed in Dead Sea water.

Maybe some of the OEM manufacturers are using something even below 400 level stainless for their 'economy car' systems now, if that even exists in the stainless steel range?

 

[mattkosem]

I hear your words. That pic doesn't look anything like meaningful corrosion, though, just cosmetic stuff. Who cares what it looks like honestly, it's under the car. Just about anything will corrode to an extent in a harsh enough environment, but 16 gauge 304 on a vehicle exhaust won't corrode to the point where there's a hole in it in 4 years.

 

[Intuit]

Not necessarily. Wall thickness (or lack there of) in addition to environmental conditions, influences the rate of oxidation. Heat, salt brine, sources of oxygen will oxidize (rust) any grade of stainless in short order.

 

[mattkosem]

High grade, true austenitic 304 stainless has to last longer than 2-3 years before perforation, regardless of the gauge, unless it is totally immersed in Dead Sea water.

Maybe some of the OEM manufacturers are using something even below 400 level stainless for their systems now, if that even exists in the stainless steel range?

Yeah, agree. The OE exhaust pipe may not be stainless at all, from the look of it, but if it is it must be some real low grade crap...and just a notch past paper thin.

--Matt

 

[mattkosem]

I am certain this muffler is stainless, and the pipes coming off of the back of it. This stuff looks like the 409 that's on our other cars. The piping from the flange on the header between everything just can't be though. 🤦 Maybe it had some coating on it, but even the spot I cut through in a cleaner area was almost entirely rust all the way though.

The Thermal R&D system fit beautifully, as one might expect, and is the super tame outcome I was hoping for.

--Matt