304 or 321 Stainless Headers?

[69TAPoser]

I am about to order my custom headers and have an option of 304 or 321 stainless. I know 321 is supposed to be "better" but what exactly is the diff. from a durability and longevity perspective? Which would you go with?

I also understand that 321 is a lot more expensive than 304, so I am also getting a price quote to understand the $$ diff.

Phil

[killer69]

321 is better under extreme heat conditions, turbo mostly, not really worth the money for a NA application .. imo

[Vicinity]

321 rusts much slower.

[deeddude]

The only difference between the two alloys is the amount of Titanium in each; 304ss containing no Ti and 321ss contain a small amount (5xC). Both contain about the same Nickel, Chrome, Iron and Manganese. I agree 304ss would be more than adequate. 321ss being better? Depends on the application, very high heat it would be worth the extra money. As far as rust, it shouldn’t rust unless it has been annealed or has been contaminated, which would be on the surface only and can be cleaned and polished off.

[80proZ]

The only difference between the two alloys is the amount of Titanium in each; 304ss containing no Ti and 321ss contain a small amount (5xC). Both contain about the same Nickel, Chrome, Iron and Manganese. I agree 304ss would be more than adequate. 321ss being better? Depends on the application, very high heat it would be worth the extra money. As far as rust, it shouldn’t rust unless it has been annealed or has been contaminated, which would be on the surface only and can be cleaned and polished off.

Everything he said is true.The reason for 321 is it is less susceptable to weld zone carburizing,in which the SS is heated to a point where it draws carbon from the surrounding air and metal.The weld will then be susceptable to rust and weld failure.

[454bug]

Hey Phil,

It depends on how you're going to "finish" off the headers... Especially if you're going to ceramic coat them... 304 will almost immediately form a "surface" rust that will continuously be there... It would be difficult to keep them completely clean long term... My buddy, J Bittle, who owns JBA headers actually builds his ENTIRE line in 304, even the headers getting ceramic coated... if you want that really pretty stainless steel look you'd have to go with the 321...

As far as durability, either one would perform essentially the same on a street car... They both will LAST forever... I plan to build mine out of 304 and then ceramic coat them satin black.

By the way, I see you're going to use the PVC mock-up process that Stainless Headers Mfg, Inc. offers... I ran across their website the other day and planned on doing the same with my car... I'll be VERY interested in hearing about how the process and tooling works. Do you actually buy the mock-up kit or do they just loan you the pieces (outside the PVC stuff)???

[69TAPoser]

Thanks guys and hi Ray. Been watching your little project (pun intended) closely for a while now.

I do plan on leaving them "raw" and don't want to have to constantly take a scothbrite to them, so it sounds like the 321 would be the way to go? (I say that BEFORE I have the pricing).

As for the process, you give them a $400 deposit that is deducted from the final bill once you send the mockup kit back. I sent my kit and my mockup back today.

As for the weld joints, they do claim to purge weld the joints:
http://www.stainlessheaders.com/customtigwelding

Here is what the mockup process looks like:




Thanks for all the input so far!!!!!!!

Phil

[WS6]

wow that's a cool way to do header mock ups! I had no idea SW did that.

[80proZ]

[QUOTE=454bug;570538]Hey Phil,

It depends on how you're going to "finish" off the headers... Especially if you're going to ceramic coat them... 304 will almost immediately form a "surface" rust that will continuously be there... It would be difficult to keep them completely clean long term... My buddy, J Bittle, who owns JBA headers actually builds his ENTIRE line in 304, even the headers getting ceramic coated... if you want that really pretty stainless steel look you'd have to go with the 321...

QUOTE]
I've never seen 304 "surface" rust unless it was physicaly contaminated by carbon steel or chemicals.Unless your building a turboed endurance race car that will see lots of abuse,321 is a waste.And 304 is pretty too,it looks exactly the same as 321.

[454bug]

I've never seen 304 "surface" rust unless it was physicaly contaminated by carbon steel or chemicals.Unless your building a turboed endurance race car that will see lots of abuse,321 is a waste.And 304 is pretty too,it looks exactly the same as 321.

All you have to do is go to GOOGLE and type in "rust 304" and you'll find many examples of it... S/S 304 is affected by Sodium Chloride (salt). As you can see, Phil lives in New Hampshire... I'm sure he experiences "salt" added to his city streets for icing issues... that residue can stay around all year long... I see you live in Florida... I doubt they "salt" the roads there very often...

You do realize that Stainless Steel still has Iron in it, don't you??? There is still a small amount of Carbon in it also... The additions of different Alloys into the iron makes up the different strains of Stainless Steel that makes the material react differently to Oxygen and it's associated oxidation... Just because the "rusting" is actually a different type of "corrosion" it definitely gives the same "appearance" of rust... just as unsightly... just a different chemical composition...

Here's one site you can check out. It's called the "Stainless Steel Information Center"... they have a lot of information pertaining to this question... Here's their website: http://www.ssina.com/faq/index.html

Here's a couple of questions listed in the FAQ section:

1. What makes stainless steel stainless?
Answer: Stainless steel must contain at least 10.5 % chromium. It is this element that reacts with the oxygen in the air to form a complex chrome-oxide surface layer that is invisible but strong enough to prevent further oxygen from "staining" (rusting) the surface. Higher levels of chromium and the addition of other alloying elements such as nickel and molybdenum enhance this surface layer and improve the corrosion resistance of the stainless material. See the "Stainless Steel Primer" for more information.

3. Can stainless steel rust? Why? (I thought stainless did not rust!)
Answer: Stainless does not "rust" as you think of regular steel rusting with a red oxide on the surface that flakes off. If you see red rust it is probably due to some iron particles that have contaminated the surface of the stainless steel and it is these iron particles that are rusting. Look at the source of the rusting and see if you can remove it from the surface. If the iron is embedded in the surface, you can try a solution of 10% nitric and 2% hydrofluoric acid at room temperature or slightly heated. Wash area well with lots and lots of water after use. Commercially available "pickling paste" can also be used. See "The Care and Cleaning of Stainless Steel" for more information.

4. What is the difference between 304 and 316 stainless steel?
Answer: 304 contains 18% chromium and 8% nickel. 316 contains 16% chromium, 10% nickel and 2% molybdenum. The "moly" is added to help resist corrosion to chlorides (like sea water and de-icing salts) See "Stainless Steel for Coastal and Salt Corrosion Applications" for more information.

Here's some information from another site called "finishing.com"... It talks about S/S 304 "rusting"...

"304 WILL rust. 304 will rust faster in hot humid climates. 304 will rust very fast in hot humid climates. Clean with a rag dipped in 30% Nitric Acid. The Nitric Acid oxidizes the exposed nickel into a contolled oxide and at the same time it removes the iron from the surface."

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

Editor's note:
Mr. Probert is the
author of "Aluminum How-To/Aluminio El Como"
--------------------------------------------------------------------------------

"By looking at the picture it is obvious that you have some pit corrosion on the surface. This is very difficult to remove! The nitric acid will not normally remove it. Some of the 304 stainless steel on the market today is not very good, but all 304ss is subject to corrosion in chloride atmospheres. Good lots of 304 should withstand the conditions you mention.

There are other formulations on the market that can help, but we have seen many situations like this recently that are constant maintenance headaches..."

Lee Kremer
Stellar Solutions, Inc.
McHenry, Illinois
----------------------------------------------

JBA Headers used to build all of their S/S headers out of 316 stainless... It made some VERY pretty headers. But, because of their competitors use of inferior, less expensive products (304 vs 316) and the use of foreign manufacturing facilities forced them to "join them" to stay competitive and start producing their product out of 304... It DOES have a "surface rust" that is noticeable and a pain to keep clean, ESPECIALLY if you live in a "salt" environment (coastal areas or northern areas that use salt on their roads)... As you can see from the answer listed above... "Moly" is added to help resist the corrosion of chlorides...


I'll agree with you that what occurs is stictly a reaction of "contaminants" on the surface of the product but it is STILL an issue to keep clean and maintenance... It's not as simple as washing it off... the porous surface of the material lends itself to contaminant oxidation... and it's NOT easy to get off...

It's NEVER so "black and white"...

[Boosted67]

I've never seen 304 "surface" rust unless it was physicaly contaminated by carbon steel or chemicals.Unless your building a turboed endurance race car that will see lots of abuse,321 is a waste.And 304 is pretty too,it looks exactly the same as 321.

Neither have I. 409 will look like that, but it have much more carbon in it than your normal "stainless." The picture shown has pitted rust, but doubt you will touch you headers 40 times a day with your palms. I would wager to say that's more of a material defect from cheap SS.
http://www.finishing.com/241/60.shtml

I think you may be mistaken though 454bug. Jay used to build his headers out of 409, which is much cheaper than 304. It's like a mild steel in it's expansion rates, but doesn't flake off in rust like mild.But it does get that appearance of rust on it. Although that may have changed since Petronix bought JBA's header line.

304 and the 321 I have seen do look the same. 316L polished is a gorgeous gold when it gets hot also, like a gold chrome.

Difference in 304 and 321 is a set of headers in 304 will cost ya 1500 bucks. 321 will cost you 1500 in material.lol I don't know that I would say one is more durable than the other as much as 304 expands at a MUCH greater rate than mild steel. Like 4 times as much I think it was. You get a header pushing around in 80 different directions, something is going to give.321 expansion rate is much closer to mild steel. So when it does expand, it's not pushing as hard in the opposite direction of another tube. Plus most of the 304 you see cracking is cheap, thin Chinese material that's under cut to hell when pulse welded.

[80proZ]

300 series stainless contians a maximum of 0.15%carbon.
304L contains .03% of carbon.
321 contains .08% of carbon.
The addition of Ti to the stainless is not for corrosion resistance,its for weld zone durability.
The chlorides your speaking of are attacking the carbon properties of the stainless.If that is the case then 304L is better than 321,as it has less carbon content.316L has the same carbon but more nickel.
I do live in Florida,and they never salt the roads,but i work in the sanitary piping industry,so i happen to know a little about stainless.
And FWIW,polishing any stainless helps alot with its corrosion resistance.

[Boosted67]

And FWIW,polishing any stainless helps alot with its corrosion resistance.

Huh, didn't know that. What actually changes when you add L to the end of a 3 series ?

[Yoda4561]

I can second the polishing helps aspect. Most of my experience with stainless isn't in cars, but on knives. A rough bead blasted or fresh satin finished cutlery grade stainless will rust almost as fast as carbon steel. Mirror polish that same blade and you could dunk it in saltwater for a few days without issue. Even high carbon steels will benefit from mirror polishing, but it's a better idea to leave the surface rough and clean to let a coating adhere properly, since the coating will protect much better than the mirror finish on non-stainless material.

[80proZ]

Huh, didn't know that. What actually changes when you add L to the end of a 3 series ?

I do beleive it means low carbon.Polishing it reduces surface imperfections that can hold contaminates.
304L is weaker than 304.But you can get 304LN,in which they add nitrogen to increase its yeild and tensile strength.
One thing i forgot to mention is that 316 has molybdenum which increases it corrosion resistance to chlorides(salt).316L=low carbon 316ss

[Motown 454]

Phil are you having 02 bungs put in the collectors just in case you get the EFI bug like I did ? Only I wasn't smart enough to do it to mine . What did they give you for a turnaround time?