Why is Stainless Steel so much superior to aluminum when it comes to exhausts?

Aluminum:
1. lightweight
2. aluminum doesn't rust.
3. affordable price
4. looks good
5. not so strong (structurally), like stainless
6. dissipates heat quickly

Stainless:
1. heavier
2. rust proof -meaning it may rust in the longrun
3. more expensive
4. looks better
5. structurally stronger
6. dissipates heat slowly


Weighing the pros and cons of each type tells me that aluminum is the way to go. On the contary, people tell me to get stainless steel, because it will last the life of the truck. ...but who keeps a truck that long anyway? 20+years? Anyone have any suggestions to change my mind why to get a stainless system?

 

I personally have not seen an aluminum exaust system???

I think the strength has a lot to do with it. The pipes and tip would be fairly thin as far as aluminum goes and over time especially when hot would get damaged from rocks and such. I would think at least.

Also the stainless looks nicer not as cheap looking.

As for the heat disapation, there may be a reason for not wanting to disapate heat to quickly under the truck. Too me that would cause problems with hoses/connectors/the gas tank under there. Just move that heat out the tailpipe. Also if you disapate heat before the cats then they won't be as effective.

Again just a bunch of guesses here but some may be vaild...

 

As for your assumptions, some of them are incorrect. All metal dissipates heat quickly. It is a conductor. Aluminum (if it exists) will dissipate equally with SS. Aluminum will not rust, but it does oxidize, which is why SS is better. It doesn't even oxidize. However, it only looks nice when it has been polished or chromed. Plain SS looks just like a brand new regular steel exhaust. As for being strong, that is why they don't make aluminum exhaust (or at least that I have ever seen). I have only seen SS or plain sheet metal/steel. I think you may be mixing up steel and aluminum. Aluminum if it is thick enough would not be much lighter than SS either. You are just used to seeing aluminum in thinner sheets than SS. Have you even ever seen an aluminum exhaust system?

 

Flowmaster makes aluminized exhausts as do other companies. I believe these are just steel with an aluminum anti-rust coating. This is probably where the confusion comes from.

 

with the heat and moisture that aluminum is subject to it would probably turn to dust in less than 2 years and on top of this it would work harden due to vibration and crack. just some observations as i've never seen an aluminum exhaust. i do see a lot of aluminum meters and transmitters that we have here at the nuc plant and all those subject to the weather have horrible corrosion problems.

 

I'm sorry for all the confusion. I should have been specific, when I said "exhaust system." I am new to all of this, and my only source of knowledge about the matter is thru these forums to form my own conclusions. As for the "exhaust system," I was referring to a "cat-back system," rather a replacement exhaust with pipes, muffler and tips, beginning from the head pipe towards the exhaust tips.
More specifically, for example, Gibson Cat-back systems are offered either in all Aluminum (with the exception of the tips), or all Stainless Steel.
As for the heat dissipation, I know now that it isn't even an issue since it was reffered to a metal that "does not even oxidize."
As for stainless steel, although I agree that it is more stronger in structure in harsh conditions, getting an aluminum cat-back will suit me just fine since I'm only keeping the truck no longer than 6 years.
If you believe that I am still confusing things, please correct me if I'm wrong. This would be a great learning experience for me.

 

I want to make a correction on my part. I misread the cat-back system description at the Gibosn Performance web site and thought it said "aluminum," rather, it said "aluminized." Thanks for clearing that up as you metioned earlier.

 

I gotta throw my $.02 in here.
The corosion resistance of aluminum varies greatly with the alloy. A 1000 series aluminum has fairly poor corosion resistance, however something like 6061 has excelent corosion resistance.

The weight of aluminum is about 1/3 the weight of plain steel, stainless is slightly heavier than plain steel.

Thickness does not matter. The only strength requirement for an exhaust system is that it must support its own weight. When I design an oxygen system that runs at 150 psi .049" THK aluminum tubing is all that is needed to meet all FAA guidelines as far as strength goes. Your exhaust system does not run at near these pressures.

Aluminum is one of the best conductors of heat, stainless is one of the worst. However unless you like hot floorboards you want to keep the heat inside the pipes.

What it all comes down to is the ability of stainless not to rust. An fully corrosion resistant aluminum exhaust system could be built but the cost would be close to that of stainless.

I don't mean to be a ***** about this. I just wanted to set things straight

 

wookie makes a good point about the different types of alloy.

stainless is also available in many alloys. borla uses 304 which is what you want. any s.s. that is a 400 serie will rust, while it is much better that plain steel and will probably not rust thru, it has a higher carbon content. if a magnet sticks, it is 400.

alum melts at around 1600 (est) while stainless is around 2200 to 2400. a true alum exhaust would have serious issues around the headers and the catalytic converter.

i had a thrush cvx system about 9 years ago, paid good money for it and it rusted thru 1.5 years and the steel tips had rust holes. i had a local shop install a flow master and the shops aluminized steel, sold the truck, still see it and the exhaust is in great shape.