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Do I Need A Stainless or Aluminized Steel Exhaust System?

Almost every exhaust manufacturer offers stainless steel exhaust systems because:

  • Stainless steel often looks better and can be polished (depending on the grade)
  • Stainless steel is very resistant to corrosion, so it’s easier to warranty than aluminized steel

The question is, are these reasons good enough for you to buy a stainless steel exhaust?

Questions To Ask Before Buying A Stainless Steel Exhaust System

1. Do I need corrosion resistance? If you live in a state where copious amounts of salt are used to melt road ice during the winter months, you should probably buy stainless. An aluminized system can survive in harsh climates, but it’s a lot more likely to rust out after 2-3 years of normal use.

On the other hand, if you live in a dry climate and/or a place that doesn’t get a lot snow and ice (and therefore very little road salt), an aluminized system can last as long as 10 years. Next, you want to ask yourself…

2. Do I want to invest in a system that might outlive my car? If you’re buying an exhaust system for a car you plan to keep for a long time (10 years or longer), stainless is a smart choice. Even if you live in a dry climate, rust can eventually work against an aluminized exhaust system.

On the other hand, you may be buying a replacement muffler for an older vehicle that’s on the downside of it’s life. If you’re driving a car, truck, or SUV that has a lot of miles, you might be wise to minimize the amount of cash you put into it and opt for aluminized steel instead of longer-lasting stainless.

Note: Stainless Steel Systems Are NOT All The Same

There are two grades of stainless steel commonly used in exhaust systems:

1. 409 stainless. 409 has become the defacto material of choice for most new vehicle manufacturers, mostly because it offers an excellent compromise between strength, resistance to corrosion, and cost. A 409 stainless steel exhaust system should last at least 8 years in almost all climates and weather conditions, but it won’t last forever.

2. 304 stainless. 304 is sometimes referred to as “marine grade” stainless because it is very resistant to corrosion from salt water. As you can imagine, an exhaust system made from 304 stainless steel can last a very, very long time. Borla, an exhaust manufacturer that is famous for offering a 1 million mile warranty, uses 304 stainless steel exclusively.

304 stainless is also nice because it can hold a polish – something that 409 stainless can’t do. Of course, no stainless steel exhaust system can maintain a polished look unless it’s very clean…which means most people will never notice the difference.

Stainless Steel Exhaust System Myths

Stainless steel lasts forever.” Not true – all stainless steel will eventually rust out. However, 304 stainless won’t rust out for at least 20 years. 409 stainless, which contains less Chromium and is therefore less expensive, won’t rust out for at least 8 years.

Stainless steel sounds different/better.” Not really…the sound difference between exhaust systems is almost exclusively the result of muffler design.

Stainless steel is stronger.” Not necessarily. Stainless can be more brittle than aluminized steel, and it has been known to crack. While the best quality stainless steel is thick and strong and shouldn’t break under any normal conditions, not all exhaust manufacturers use the best quality stainless.

Stainless steel won’t stain.” Wrong. Despite it’s name, stainless steel is NOT stain proof. 409 stainless, in particular, will often take on a reddish hue. 304 stainless steel can discolor under extreme heat, and may not always polish back to the original shine. 304 stainless can also become pitted.

Bottom Line: Stainless steel exhaust systems are often a smart choice, but there are plenty of good reasons to buy an aluminized exhaust instead. If you do opt for stainless, be sure to check if you’re buying 304 or 409 stainless

45 Comments Post a comment
  1. Jonny Davison
    Feb 5 2012

    What is the Weight Difference between Aluminised Steel & Stainless Steel?

    Reply
    • Jason
      Feb 21 2012

      Jonny – Good question! Stainless is just a bit more dense – 316 grade is 8,000 kg per cubic meter vs. 439 grade aluminized which is 7,695 kg per cubic meter…or about 4% more dense. However, the tubing in the typical aluminized system is just a bit thicker than the typical stainless system tubing, so it’s probably a push.

      If we look at shipping weights on two identical MBRP cat-back exhaust systems (model # S5212AL and S5212304), the shipping weight on the 304 stainless system is about 3 pounds lower…and that sounds about right. For almost all intents and purposes, the weight difference is negligible.

      Titanium, however, is another story…you could save almost half the weight of the system going from 304 stainless to titanium (which has a density of about 4500 kg/m3). That’s why it’s used in expensive performance cars where every pound counts.

      Reply
  2. Edgar
    Mar 20 2012

    How about the weight difference of 304 stainless and aluminized steel?

    Reply
    • Jason
      Mar 20 2012

      Edgar – The answer to your question is the same as the one above. No appreciable density difference between 304 and 409 stainless.

      Reply
  3. Larry
    Aug 14 2012

    What about dissimilar metal corrosion if you don’t have a full aluminized exhaust? Also I’ve noticed a lot of manufacturers don’t note the type of stainless steel they use most only refer to the exhaust tips, which I’ve noticed most exhaust tips are T-304…

    Reply
    • Jason
      Aug 20 2012

      Larry – I’ve not heard of any corrosion issues due to dissimilar metals in an aluminized system, only I’m sure that it can happen under the right circumstances. It’s a bigger concern in a marine environment than it is anywhere else, but it’s all about time…if you need your exhaust to last more than 5 years, it might be worthwhile to invest in stainless.

      Having said that, aluminized systems can last practically forever in dry climates.

      As for manufacturers not sharing the grade of steel they use, assume that it’s 409 stainless unless otherwise noted. 409 stainless is the de-facto material for most new cars as well.

      Reply
      • Dec 3 2015

        I have some excellent pictures showing galvanic corrosion of a muffler constructed with SS endcaps and middle wrapped with aluminized steel.. In less than one year, the aluminzed cover fell off, as it corroded away from the crimped joint on the end with the SS.
        this muffler operated in Northern Vermont.. lots od snow and ice and salt here…

        Reply
  4. Dom
    Jul 2 2013

    I plan on upgrading my exhaust soon. Just wondering if I should go with stainless as I only plan on keeping the car for 2-4 years. I live in Chicago, and will be going with flowmaster super 44s.

    Reply
    • Jason
      Jul 2 2013

      Dom – Aluminized sounds like the way to go if you only need the system to last 2-4 years.

      Reply
  5. John Yuhaschek
    Feb 28 2014

    Is 304 stainless steel easily bent in an exhaust shop? Is it brittle? Do I need to weld it differently than aluminized steel?

    Reply
    • Jason
      Mar 2 2014

      John – To my knowledge, there’s no structural issues with bending 304 stainless compared to another grade of steel. If you have the right tools and process, you’ll have no trouble.

      Reply
  6. abood
    Jun 3 2014

    what about the heat resistance between aluminized and stanless ?

    Reply
    • Jason
      Jun 3 2014

      Abood – To my knowledge, aluminized steel and stainless steel hold up to heat about the same (at least as far as exhaust systems are concerned).

      Having said that, stainless steel will “blue” under heat. Some people like this, and some don’t. The bluing can be polished away if it’s a problem, but it will have to be done often unless some sort of treatment is used.

      Reply
      • sid
        Mar 5 2015

        You get heat resistant paints if you want more resistance to heat mate!!

        Reply
  7. Dan
    Jul 2 2014

    Will aluminized steel last long (5-7 years) in the Florida climate?? It rains a lot but no snow.

    Reply
    • Jason
      Jul 7 2014

      Dan – Probably, but no guarantees. If you’re close to the beach, the saltwater in the air can corrode systems quickly without any temperature variation.

      Reply
      • John Faiella
        Sep 25 2016

        I live in north central Florida. The high humidity is a concern for rust. Which one do you think would be better for my classic car?

        Reply
        • Jason
          Sep 26 2016

          John – Since it’s a classic, you probably want the exhaust to last. I’d go stainless all the way.

          As to the grade, either is fine.

          Reply
  8. Eythan
    Jul 9 2014

    Thanks for the info, I truly appreciate it. I was looking for a way to modify my car, and a full exhaust system seems best, sinc I plan to stay N/A for now.

    You have very clearly illustrated the difference between aluminized and stainless. As I will only have my car for another 2 years, aluminized seems the way to go.

    Just wanted to say thank you for offering your advice on a topic I barely understand.

    🙂

    Reply
  9. Leo
    Aug 29 2014

    I live in southern California in the low desert valley, doesn’t rain much; was wondering which kind of steel I should get for my cat-back exhaust since my stock exhaust has rusted out?

    Reply
    • Jason
      Sep 1 2014

      Leo – If it’s dry and rust isn’t generally a concern, aluminized is fine.

      Reply
  10. Josh
    Dec 9 2014

    I live in Kansas, and am debating on getting a stainless steel exhaust or an aluminized steel on my pickup. We have a good amount of snow in the winter and a lot of salt but i try to keep my truck clean when the temperature allows washing. What would you suggest for the longest life of a system between these two?

    Reply
    • Jason
      Mar 3 2015

      Josh – Even outside the so-called rust belt (NE USA and Canada), I’d still go with stainless. The cost difference is small compared to the increased life of the systems.

      Reply
  11. John Y.
    Mar 3 2015

    304 Stainless is a bear to cut through. If using a cutting tool, 1 Carbide Blade = 2 cuts through 16 guage pipe. I live in PA where we use a lot of salt in the winter. Just looked (March 3rd) at the underbelly of the car and found the 304 SS still looks shiny (never polished). For the money, I’d go with 304. I got 2 7ft. pipes of 304 SS 16 guage 2.25 inch from Moore Performance (http://mooreperformanceparts.com) for $100/each = Total of $200. I don’t plan on keeping my car for 20 years, however it’s a good selling point when I sell my car that the exhaust won’t rust out anytime soon.

    Reply
  12. Rob
    Mar 15 2015

    I see a lot here about ambient conditions (temperature, rain) but driving a vehicle for short periods will not permit the exhaust to fully warm and condensation will form — so your exhaust can rust from the inside out, even if the exterior is okay. I’ve used protective exhaust paints on both the inside and exterior of exhaust systems — they do not seem very effective. My 2002 Nissan Pathfinder goes through an exhaust about every two years. I would have opted for a top-grade stainless system but sadly, I can’t find one to fit it. It would be great if I could fabricate one but it’s beyond my skills level.

    Reply
    • Jason
      Mar 16 2015

      Rob – An excellent point. If you don’t drive your vehicle long enough for it to reach normal operating temps, the exhaust can rust from the inside out.

      Also, 409 stainless systems ought to be available from Nissan…is the OEM system no longer available?

      Reply
  13. Bob Landry
    Mar 20 2015

    Time for a possible dumb question…Could spraying the underside of the car during the salt months regularly be of any use to extend the life of aluminium exhaust? Thanks

    Reply
    • Jason
      Mar 21 2015

      Bob – Absolutely yes. Not a dumb question either, as a lot of people don’t know to do this.

      Reply
  14. Ricardo
    Apr 21 2015

    A MBRP Aluminized exhaust system is more durable that the original ford fiesta St exhaust system. I live in Puerto Rico, we do have variable weather, but is more dry than rainy. It would be a wise decision instead of a T409 to go for the aluminized system ?

    Reply
    • Jason
      Jul 20 2015

      Ricardo – I highly doubt an aluminized after-market exhaust is more durable than the OE exhaust on a new Fiesta ST. If you go that route, don’t be surprised if the replacement exhaust wears out even faster than the factory exhaust.

      Also, your factory exhaust might be covered under the federal emissions warranty…I’d suggest you go to the Ford dealer and ask them to get it covered. 🙂

      Reply
      • Tom Chandler
        May 18 2016

        I ve been thru two Walker aluminized mufflers in past 23 months. These are advertised as Stainless,, but only the end caps are SS,, the body is wrapped in aluminized steel and it fell apart where the two metals touch, in classic galvanic corrosion… will never but another walker… these are junk.. the OEM on my 205 Nissan lasted almost 10 year… live in Northern VT – use a lot of salt here but the construction of these Walkers is really subpar.. the SS is crimped over the aluminized section breaking thru the aluminum coating exposing the bare steel underneath that falls apart in short order.. Walker needs to have an engineer on their staff involved in muffler design. I have posted this story with pics on LinkedIn with a lot of supportive comments from corrosion engineers and metallurgists

        Reply
        • Jason
          May 18 2016

          Tom – It’s not at all uncommon. “Aluminized” steel isn’t very corrosion resistant. The best system to buy – and what the OEMs use – is 409 stainless.

          As for Walker, they make all kinds of exhaust parts. They make OEM stuff that lasts 10 years, and they make cheap stuff that rusts out in 2 years. Sometimes, you get what you pay for. 🙂

          Reply
          • Tom
            Oct 3 2016

            I agree, this was an inexpensive muffler and I would have been happy to get 3 years of use from this muffler on my 11 year old Altima as others have stated.
            With some different construction, perhaps it would… the aluminized section will last as long as there is no exposed galvanic couple exposed to the harsh environment. I was shocked when this literally fell apart in just under one year.

  15. Mike
    Jun 16 2015

    Hi, I haven’s seen any question’s like mine so I’ll ask away…I have heard some great sounding S.S exhaust systems perhaps the S.S is thinner than Aluminzed Steel? but it just seems to me that they “sound” different (better) what’s your opinion regarding this?

    Reply
    • Jason
      Jul 20 2015

      Mike – I recall someone asking something similar, but I don’t know that there was a definitive answer.

      My opinion – one that I haven’t tested – is that the natural resonant frequencies of alumnizied and stainless systems are slightly different. But could the human ear detect them? Beats me. It’s got to be small, whatever it is.

      So I’d say probably no difference…but I’d love to see someone test that.

      Reply
  16. Kobe
    Jul 7 2015

    I’m about to run flowmaster super 44 on my 96 bronco and I was wondering if I should go stainless or aluminezed I live in Tennessee

    Reply
    • Jason
      Jul 20 2015

      Kobe – Stainless would be my recommendation.

      Reply
  17. Vann
    Dec 7 2015

    Hi,

    I live in Malaysia, a bit north of the equator. It rains 40% of the time here but I live far from the ocean. No snow, of course. Temperature ranges between 26’C to 35’C. Suggestion?

    Reply
    • Jason
      Dec 8 2015

      Vann – Stainless steel all the way.

      Reply
  18. Terrell
    May 18 2016

    I live in Canada, where it snows often and snow is on distributed on the road. I plan to keep my car 3-6 years. Aluminized or Stainless?

    Reply
    • Jason
      May 18 2016

      Terrell – Stainless.

      Reply
  19. Christine
    Jul 22 2017

    Big Thank You for putting up this great information to help us decide the best for our cars.

    I have a 1999 Blazer that I hope to keep for a few more years that is in need of new exhaust aft of the catalytic converter. I live in the northern half of Idaho where we do get snow. Anti-icers using magnesium chloride and corrosion inhibitors are applied along with sodium chloride being sometimes used but not nearly as much as in the North East. Would an aluminized system be appropriate for me?

    As a point of reference, I only have surface rust on the underside of my truck as opposed to the deep corrosion I saw on many cars when I lived in northern IN and central VT.

    http://itd.idaho.gov/road-mtce/
    http://apps.itd.idaho.gov/apps/info/Brochure%20-%20Salt%20small.pdf

    Reply
    • Jason
      Jul 26 2017

      Christine – My opinion is that alumnized is always best on older vehicles. Your plan is to make the ’99 live for a few more years, but there’s always a chance that it will break down and not be worth repairing.

      Also, as bad as corrosion can be in a place like Idaho, it’s not nearly as big of a concern as it is closer to the ocean…humidity + salt in the air = rapid corrosion. Take the salt away, and the rates are lower.

      In fact, if you wash the underside of your vehicle very couple of months during the winter, you can probably prevent corrosion for several years.

      Additionally, I think mag chloride is harder on stainless than on aluminized…only I don’t know that with certainty.

      Reply

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