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Car Muffler Discoloration

Hello, so I noticed that my muffler started to turn brownish on my 2014 Corolla. I am worried because my car only has only 480 miles. Is this normal, should I be worried?


That’s a little surface rust from the weld. Not a problem.

The seeds of rust have sprouted. It’s all downhill from here on out. No car makes it out alive…

"I am worried because my car only has only 480 miles. Is this normal, should I be worried? "

Yes, it is entirely normal for that to happen.
I have to assume that this is the first car that you have ever owned, as…virtually everything…about the car seems to worry you at this point.
Am I correct?

I strongly suggest that you read the Owner’s Manual from cover to cover over the next few days, as it will familiarize you with most things that you need to know about the car–including how to tighten the gas cap.

No, it will not discuss things like rust discoloration on the muffler or the potential for a car to roll on an incline, but it will give you some very helpful information on a wide variety of topics related to the operation and maintenance of your new car.

My 2006 Matrix muffler looked 'bout like that when I got it in 2007; still looks almost the same today.
It’s stainless steel and should last.

It’s not stainless steel. It’s aluminized steel.

If it were stainless steel, that weld would have been made with MIG welder using stainless steel wire or TIG welder using a stainless steel rod.

But since the weld is rusting, it tells me that the weld was made with carbon steel wire on aluminized steel.


@Tester‌ so in conclusion, I shouldn’t worry about the rust?

For the record…stainless steel used in exhaust systems will still rust…just no where near as fast as they use to. There are levels of stainless steel.

No, you shouldn’t worry about it.
If you do an informal visual survey of the newer cars in your neighborhood, you will see essentially the same rust discoloration on the muffler weld marks of most–if not all–of them.

And, please allow me to be a bit pre-emptive at this point.
If you observe rust on your brake rotors, that is also normal.

When conditions are very humid, it is not unusual for the rotors on many cars to develop a surface coating of rust overnight.
Again, this is nothing to be concerned about, and after a couple of stops, that rust coating will be worn away–albeit with some squeaking noises.

If it still bothers you (and I know it does), just buy a can of this:

Wire brush the rusty areas then spray it with this when the mood strikes you.


It’s normal for rust to form on a weld bead if it’s not protected.


Yes. The metal used in the muffler is stainless; the weld bead isn’t necessarily. That’s why you’re starting to get rust at the welds.

In another 25 years or so, it’s likely your muffler will fail at the weld, if you live in an environment where they use salt in winter.

It’s normal. Coincidentally I was under my car a couple wweeks ago in that area (looking at the rear suspension) and (an early 1990’s Corolla) muffler looks nearly the same as your photo. It’s the original muffler. I think most of the rust appearance must occur fairly fast, then it stays the same for quite a long time. The muffler and tail pipe will eventually rust through and fall off if you don’t fix it beforehand, if you live in an area that uses salt on the roads due to snow. Even if it happens, its nothing to lose sleep over. It’s a relatively inexpensive fix. Otherwise, if you live in a mild winter climate, you’ll probably be fine for 20 years or so. I used to live in Colorado and had to have exhaust components on my truck replaced fairly often, every 5 years or so, due to road salt corrosion. Ever since the truck has been in Calif, since there is no salt on the roads, that hasn’t been necessary. You can spray that area with a hose when you wash the car if you like, that will wash away road salts, but if you do drive it around the block so it heats up and evaporates any water from the hose.

@idrivea2014Corolla–The Toyota Corolla may not have been the right car for you. You are a worrier and Toyotas are generally so trouble free that there isn’t anything to worry about. Then you will be worried that you don’t have anything to worry about.
The muffler on your Toyota becomes hot when you run the car and then cools off when you park the car. This causes the discoloration. I bought a new charcoal starter chimney at the beginning of the season. I put the charcoal in this starter chimney. There is a grate going across the chimney and the charcoal lies on top this grate. I crumple newspapers at the bottom of the chimney and light the crumpled newspaper. This then starts the charcoal. The charcoal chimney becomes discolored after the first use from the heat of the charcoal. Yet, I can get about 3 years from this $10 item. Your Toyota muffler is built of better material than my charcoal chimney and will last much longer. Quit worrying and enjoy your mew car.
If you need something to worry about, I’ll send you a list of the cars I have owned that I bought as used cars. These cars gave me plenty to worry about.

I’ve got a 95 that every once in a while I’ll paint the backs of the dual exhaust to make it look nicer because it shows. Fully warming the car up will warm the mufflers up to dry them out to reduce the chance of rust. Nbd though.

What you’re seeing is perfectly normal and absolutely nothing to worry about.

Stainless steel is basically just regular steel (iron and carbon) with an additional metal alloyed in to retard oxidation. Various alloy metals are used, the most common perhaps being molybdenum. The area around weld joints, known as the “heat affected zone” (HAZ) is affected by the extreme heat applied to melt the base metal. Heat that hot does affect the structure of the alloy. Some discoloration and is common. Welders purge (wash) the area with a “backing gas” (an inert gas that prevents the effects of oxygen on the melted steel), but there’s still often discoloration. The amount of discoloration varies with the exact SS alloy, the purge gas, the filler used, and some other factors, but it isn’t abnormal.

Bottom line: I’ve spent more time under my car, and cars in general (including Corollas), than the average layman, and this is perfectly normal. My current car, a Scion, has the same discoloration… and it has over 217,000 miles and nine years on it and the exhaust is still in great shape.

A good friend’s 2002 Corolla developed an exhaust leak (original parts) this summer and when I got under the car I discovered that a bolt holding a joint bracket (called a “V-bracket”) had rusted away allowing the joint to leak. The exhaust was still fully solid and in excellent shape. I fixed the V-bracket, replaced the steel gasket (just to be certain) and the system was as good as new.

Sleep soundly. Your exhaust is fine. A tip of the hat to you for paying attention to your car. Keep up the good work and the car will serve you for a very long time.

It’ll last a lot longer than the older ones. My 79 Corolla used to need a new one every summer.

Soon you’ll get your first door ding in a parking lot and forget all about the muffler. Sorry.

I would be more concerned if the muffler did not turn brown because it’s completely normal.