View Full Version : Grades of stainless steel
huntindog
04-13-2003, 19:29
I see that there are several grades of stainless used in aftermarket exhausts.
Does anyone know what grade comes stock from GM?
I believe the most common SS used in exhaust is 304SS, as you will find in the corvette.
[ 04-13-2003: Message edited by: 62dog ]</p>
Lone Eagle
04-13-2003, 20:27
Our GM Dmax has an aluminum coating on mild steel. Later! Lone Eagle ;)
KompressorMan
04-14-2003, 05:36
Lone Eagle, The O1' brochure describes the exhaust as Aluminized stainless steel.
Herb
ok mac..........where are ya?..... :D dave
There is a controversy over whether our Dmax is full 409 (cheap) stainless or aluminized mild steel. I think it's 409.
The new corvette has titanium exhaust.
I don't think any manufacturer offers 304 SS exhaust except maybe at the heads.
304 is the good stuff.
The best way to see this is on a gasser. The pipes through the catalyst are 400 grade stainless. On outr Duramax diesels, the pipes feeding and exiting the turbo are 400 grade. The balance of the stsyem is aluminized mild steel.
The SS exhaust claim on the window sticker is a blanket statement as is "platinum spark plugs"
REAL stainless systems are 304...
I don't know about that ;)
The tail pipe "tip" does not look like aluminized staeel at all. It looks like stainless and doesn't have that silver "aluminum" coating. Why is that? You can polish it up. I don't believe you can polish aluminized without removing the dull aluminum layer.
Dunno,
I have an almost brand new system laying out here and it looks to be the same from front to rear. Chances are, road spray has altered the appearance. Why would someone coat a stainless pipe?
CleviteKid
04-14-2003, 12:00
409 stainless, the cheap stuff, just barely meets the definition of stainless, that is steel with 11% or more chromium.
The good stuff, 304, has 18% chromium and 8 % nickel. Both alloying additives are EXPENSIVE compared to iron.
They have a saying in the auto industry, as the price of nickel goes up, the corrosion resistance of 409 goes up ;) .
Since 409 will tarnish and pit and actually show red rust stains in some circumstances, it is occassionally coated with aluminum to preserve its appearance. Still cheaper than solid 304 for your exhaust.
Buyer beware.
Dr. Lee :cool:
huntindog
04-14-2003, 13:50
WOW, response from all over the board.
I'm not sure what to believe at this point.
The reason I posted this is I'm starting to get serious about an exhaust.
I live in arizona, so what ever I get will last forever.
I do know that aluminized steel will eventually surface rust here.
I don't really like the looks of a rusted pipe.
I have heard of some people who are polishing their pipe, so I figure it is probably stainless.
Whatever I get, I don't want a downgrade in material from stock.
As of right now, I'm thinking that 409 would work in my climate.
JK, when do you expect yours to be ready?
I'm trying to remember who I sent them to. I was thinking that at least one was to a forum member. I had a local guy due in for an install, but he cancelled, and I've been too busy with the fuel filter project (and spring riding season) to pursue him to reschedule...
BlackMax
04-14-2003, 14:21
The auto industry does not use it but really good stanless is 316, it will not rust at all. 304 will get small rust spots and tarnish when it comes in contact with some chemicals and atmospheres. 400 as sme others have said is a lower grade than 316 and 304 and will tarnish and pit more. It also degrade more from the acids in exhaust gases but not as much as mild steel.
WillowCreekStable
04-14-2003, 15:10
Now that spring seems to have arrived up here in the snowy north, my thoughts have turned to exhaust systems. Sure fire sign you are getting old when that
Hmm, let me think ~ "...The O1' brochure describes the exhaust as Aluminized stainless steel." I think the same is in the '02 brochure.
Does that mean it has stainsless qualities based solely on a thin layer of aluminum? Akin to the term 'Gold Filled' meaning: Gold, Filled or really gold plated. Nothing changed just the wording. Alas, me suspect there are some wordsmiths at work on our DuraMax's.
chicoc48
04-14-2003, 16:22
Check out the post just down the board from here titled "Exhaust system". There's a link in there to a full T-304 system. Looks NICE... FWIW- I had a cat-back Borla on my '99 half ton (supposedly 304) and the pipe from the flange back to the muffler was definitely discolored/scaly after 2 Wisconsin winters. The muffler and on back was just like new however. I'm not sure we can expect any kind of stainless to remain new-looking for an extended period of time. It's just a nasty environment under there!!
my .02 :D
chico
Lone Eagle
04-14-2003, 18:59
I know that a madnet is not the best test. I have some stainless bolt in the bin that are not magnetic and I have some that are just a little. My telescoping magnet will hang off the tail pipe. Damm little stainless I would say. Later! Lone Eagle :D
chicoc48
04-14-2003, 19:09
Ok, just to stir things up a bit, here's what Banks has to say:
What grade of stainless steel does Banks use in its exhaust systems, and why?
Today, there are quite a few exhaust systems available on the market, and they are constructed from a variety of materials including aluminized steel and various grades of stainless steel. You are wise to avoid those built of aluminized steel. Aluminized steel is somewhat prevalent because it is cheap and relatively easy to bend. The aluminized coating on the steel will begin to break down at about 1100 degrees
KompressorMan
04-14-2003, 19:21
I have heard of some people who are polishing their pipe, so I figure it is probably stainless.
HUNTINDOG!!! You da Man :D :D :D Sounds like Lee Majors from the Six Million Dollar Man
Mackin, yo turn
I really think it's 400 series stainless.
Aluminized steel is easy to identify. It has a cheap looking aluminum coating and the seam usually gets rusty.
Our exhaust does not have that aluminum look to it and if you take a brillow pad or sandpaper to aluminized, you'll remove the coating and rust will form. No so with our exhaust.
The OEM system is 409.....I'll shoot right out of the closet and say it.....Five or six years ago,or longer, all manufactures changed to 409 .... Other wise with the added warranties on these vehicles everyone would be barking for a new system...Take a look at your front driveshaft...I'm thinking of getting a new one ..... tongue.gif
Type 409 although a stainless is low grade Stainless....Forget nickel content for this argument, cause no one wants to, one cold reduce to harden, Two consider heat reliability or Three deep draw an exhaust system, or put the corrosion capabilities really to the test..... :rolleyes:
409 (439 is better) is chosen for it's ease in bending and welding capabilities and cost....It will out live any Aluminized system especially at the "welds"....
Aluminized steel is only a coating on the exterior.....The Cold Rolled steel (refereed to her as mild steel) will rot from the inside out,NOT recommended for gassers at all...Yes,diesel do not create the moisture gassers do, but they do, and the process is slower...... I am also not saying it won't last...But it won't last as long.....Buffing and or cleaning up of tailpipe if desired isn't an option....
Higher grade stainless 300 series (all L grades, low carbon, will last the longest by the way, for corrosion, especially 316 L or 317 L) are expensive, very market driven and is a commodity.....
Harder to bend,weld,demand a higher price ETC.... It will stain due to some, if not most environmental conditions....
Yes, this would be the prettiest no doubt.....But would require maintenance as other SS add-ons to keep it that way.....If I were out of the snow belt I would consider....
Both 300 series and 409 systems will last a very, very long time......When the day is done and you peek back at the tailpipe and it's all dirty, you'll feel a lot better knowing you paid for 409,which I would recommended ..... Plenty of cash left for Scotty brites,for a spiffy tailpipe(s) which is all your gonna see anyway..... :eek: :eek:
I can supply samples and certs. of compliance...Spank you very much......
MAC
WillowCreekStable
04-15-2003, 09:04
Well glad to see this is cleared up...... :rolleyes: :rolleyes:
Got some old 5" cast sewer pipe behind the barn. A bit tough to bend.....
For me, it might come down to price to install and how long I plan to keep the truck. Living in the rust belt I think they will all get a bit ratty looking after a few winters.
Look at the OE downpipe. It is made of 2 different materials. The first collar is bare, and the rest aluminized...
I'm gonna use 6" PVC DWV pipe. Schedule 80 for stiffness.
Since there's not much heat, it should work fine and never rust. They got grey, white or aqua green.
"Look at the OE downpipe. It is made of 2 different materials. The first collar is bare, and the rest aluminized..."
He Heee good one and the exhaust manifolds are,besides rusty ??? :rolleyes:
Can any one truely replace the "turbo down pipe" ?? No .....
But the first pipe leading off of it that the V flange connects to is 409 like the balance of the exhaust system,OEM.....
This is why I stayed away from this topic in the beginning...... I wish I continued to,honestly.... :(
Bottom line, 409 is better then aluminized,it can't be denied.....Type 304 is better then that,but you'll pay a premium..... A premium you will only see the majority of when your changing your oil .....
MAC :(
Go with HOOT plastic....... smile.gif
Cast iron is way to heavy ...... :rolleyes:
Manifold to turbo = 409ss there's really no denying that.
Turbo to Vee clamp is also same material.
The first 3" section exiting fromn the Vee clamp is also 409, but the rest of the system is aluminized. I wonder why?
The gassers are bare 409 till the muffler which is aluminized as well as the tailpipe. I SERIOUSLY doubt that the pipe under that coating is stainless. I have a pic of an apparently defective OE tailpipe with a large spot of rust. I know 409 would not do that as aggressively...
I'm going by what I was told, in the steel industry, that the big three has changed over to Stainless...... I'll see if I can firm it up......If the Duramax is still CRS aluminized so be it .....
I think what your seeing is the result of heating forming and welding in that short piece brown in color...... The short off color section, as oppose to the balance of pipe gray in color,mics .075 thick as does the balance of exhaust system, uniform in thickness .... Check it out yourself....
Take a look at the hangers ...I guess right under the hangers is 409 also along with the hanger itself..Same color as the 3" section, after welding forming etc......Take a file to any section of OEM exhaust, check for a coating ..... If I wasn't saving I'd hack a piece off and send to a metallurgist .... Anyone want to hack me off a piece ?? I send samples to labs every day .... Need but a small piece 2" square or round .... Nothing to long physicals will not be necessary just chemistry .... In addition, Stainless all grades come in numerous finishes,from matte to mirror....
Not looking for an exhaust war..... Cold rolled Aluminized is OK .
As I recall, the basic premise was Fed enviromental laws requiring emission control components to be warrantied to 5/50,000. The change over to stainsless may have been to midigate early failure of the exhaust system. BTW, my diesel rabbit has orginal exhaust system ~ yeah, kinda loud but no holes ~
Devin Tornow
04-15-2003, 21:00
Wow, I never heard so much talk about Stainless.
Here's a good links about the material & construction.
http://burnsstainless.com/TechArticles/techarticles.html
http://burnsstainless.com/TechArticles/Stainless_article/stainless_article.html
OK, let me throw another one at this.
Guy here at work just brought in a brand new Dodge Hemi 4x4 HD.
I looked at the exhaust. Looks a little like aluminized steel just like JK said about the Dmax.
Stamped all along the side of the pipe is a number...
409 and some other jibberish. If anyone wants the rest of the numbers, I'll get them.
a64pilot
04-22-2003, 11:32
oyazi,
In the south it is common for Diesel exhausts to outlast the vehicle. I believe it is because the exhaust is essentially coated in rust prevantitive on the inside so they have to rust from the outside in.
JMJORDAN
04-22-2003, 17:51
I been watching this post for a while. I thought I should get involved. I am Tool and Die Maker (Precision Machinist) I also have a degree in Metal Engineering. Some of the companies I have done work for are General Motors, Delphi, Boeing, Mercedes Benz, Cannon, Harley-Davidson,and Cooper Bessemer. The company I work for makes tooling, dies, molds, assemblies, and gages.
Now that you know to much about me.
I recently cut the last 3" off of stock tail pipe (I have pics to prove it! )and sent them to friend who works for Metrolgy company for analysis. I did not tell him what I thought it was. He returned piece to me today and said that is was 410 stainless steel. The test he performed was a Spectural Analysis. I am not trying to stir up storm but trying to add closer to this debate! :D
JMJORDAN
That's interesting ... Type 410 is an alloy used for the most part in the application where parts are stamped then heat treated.... Type 410 is also harder in the annealed condition therefore harder to bend, in addition higher tensile, and is higher in cost for raw material .... This sounds to me where a substitution was used during production if they were to get caught, that would be another story in it's self .... Believe it or not this happens a lot in the industry..... Not a problem although, not as good as 409 in corrosion protection, due to higher carbon content, but better then aluminized CRS nevertheless .... Thanks for the info ......
Heres some info for you gents,pro aluminize ..... I have checked my stock system for aluminized coating and see none ..... The Banks also has no aluminized coating .... Not sure where they got their Salt test ,but looks to me that this sample was dragged thru the Red Sea for awhile......Probably high end OEM exhaust systems, Vette comes to mind .....
Type 409/439 HOT dipped aluminized,inside/outside coated ....
=>http://www.aksteel.com/pdf/markets_products/carbon/Aluminized_409-439_Data_Bulletin.pdf
Again if someone hacks me off a piece I'll have it tested .......
MAC
[ 04-22-2003: Message edited by: mackin ]</p>
JMJORDAN
04-22-2003, 19:31
Mackin
You are right substitution is common in the manufacturing industry. I was guessing it would be 409 or 416 to be honest. Now we know that are exhausts are stainless. I would be happy to send you mine if you wanted to try it for yourself. ;)
SPectral analysis baby. Put that one to bed....
I have a chemist friend that works for a Dupont spinoff that makes fuel additives.
I gave him a bottle of FPPF Total Power. So far, initial results show it as being mostly cetane boost.
He is going to have Gas Chromatography/Mass Spectrometry done on it to determine the elements present.
I cannot remember how to spell it.... :rolleyes: but I think that the Stainless Steel that I'm thinking of is call Hastroloft. This is the steel they use in "HIGH HEAT" applications such as a furnance. Would it be worth useing?
Burner----> :D
I think your referring to hastealoy.....
Your thinking of the high end "Nickel Alloys"..... Waspaoy,Monel and Inconel etc. Inconel which is used in Annealing furnaces,tubes could with stand some heat....Lets just step right up to Nickel/Chrome that's what we really desire .... Price any of these and you'll see how fast you settle for 409 and scotch brite pads ......
MAC
:D :D :D
Amianthus
04-23-2003, 08:14
mackin, how's it that you know so much about metalurgy? (But you still drive a GM? tongue.gif :D )
I've been following this a little (I'm an ASME AI) and have to agree with what's been posted. Although, I don't think most can afford the exotics like the monels, inconels, austinetics, hastelloys, etc. BTW, doesn't the Ni/Cr alloys suffer from Cl- stress corrosion problems (road salt)? I can't remember.
I do have a client that welds out titanium heat exchangers. But I can't fathom how much that would cost to make an exhaust outta the stuff. Would be neat to see though.
[ 04-23-2003: Message edited by: Amianthus ]</p>
john deere
04-23-2003, 10:42
It's 409 that is on your truck. Period.
Amianthus,
The Z06 Corvette comes with titanium exhaust....
STOCK!
And believe it or not, entire dual aftermarket 100% titanium systems for C5 Corvettes are under $2000. One system is $1325.
Titanium has come down in price a lot in recent years.
Read more here....
http://corvetteactioncenter.com/specs/z06/z06exhaust.html
[ 04-23-2003: Message edited by: hoot ]</p>
Amianthus
Why do I drive GM ???
Cause they let anyone drive a dodge ..... tongue.gif tongue.gif
Stainless strip is my lively hood ..... Cold reducing, up to spring temper, no intermediate anneal is my bread and butter.....Over 20 years experience ...... Owner, sometimes operator, not afraid to get my mitts dirty ..... I don't play with the exotics,high nickel .... All grades of 300 series + 201 and 17-7 ph and 400 series .....But I can get what anyone may desire .....
Hand grenade springs,They just need to use more of these ....
MAC :D :D :D
Amianthus
04-24-2003, 09:03
"Cause they let anyone drive a dodge."
You better say that with a capital "D".
(Keep the gloves up) :D
Stainless is your bread and butter eh? We don't deal with much stainless around here. Except for the transition joints used on these heat exchangers. Aluminum is what I have my experience with lately. In cryogenic service (-400F), Aluminum really shines. But stainless is the best material to mate to, to limit the galvanic corrision that takes place in the processes that the HX's are used in. Nothing but 304 and 304L. 1" thick at times. Some pretty neat stuff, I might say.
I was unaware that the 'Vette exhausts were titanium. You really gotta know what you're doing with the stuff. Not just any hunyuck can work on it. Sounds cool though. Super strong, light, corrosion resistant, heat resistant. What could be so bad, outside of the special fabrication requirements.
Well all I will say is that from the short stub after the Vee clamp to the remaining system after the weld there is a DEFINITE material change. The first 3" pipe looks just like the factory turbo feed/outlet pipes, and the rest has the appearance of an aluminizing or galvanizing on it. This is on a 1100 mile Dmax exhaust system that still appears new...
Maybe what is under that coating IS stainless steel, but I really gotta wonder why one would coat a pipe that would not rust...
John,
I did some research on 409 SS. It is nothing special. It's not a whole lot better than aluminized non-SS. That's why it discolors and yes, can rust. Just not as prolifically as non-SS.
I believe the SS from the engine to the "V" at the bottom of the downpipe is 304 SS. From there back it's 409.
I believe the muffler itself is not 409.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.