304 or 409 stainless exhaust

[longbed67]

I am torn right now between the 304 or 409 ss mandrel bent exhaust I can get a full kit will all the mandrel bent pipe for my truck for these prices.

304--- $302.75 shipped to my door

409--- $208.75 shipped to my door

Is the 304 worth the extra $100 bucks if so why? I will be doing all of the fitment and welding myself so the only other cost will be the filler rod to tig it up.


http://www.mandrelbendingsolutions.c...-SS/Categories

[Spartan]

Without getting to technical,and correct me if I'm wrong, but I believe the 304 is the better material. Both types of stainless are good. Since you are TIG welding it yourself you probably know the heat will "color" the material. My 2 cents.
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[JJorgensen52]

409 is a lesser grade of stainless - it will form some surface rust which seals it and prevents further corrosion, but it's not pretty to look at once it's been out in the air for a bit. 304 has better corrosion resistance.

[longbed67]

correct 304 has a higher chromium content and 304 will heat discolor, and 409 will discolor and get a light surface rust when left to the elements, but this will only be driven in the summer. I am familiar with the material properties, and new exhaust systems are commonly 409 I guess I am asking for opinions, thoughts, and personal experience with both...

[Lattimer]

409 is typical for exhausts on newer vehicles. Because of how lean new vehicles run, they have a large amount of condensation in the exhaust. Combine with oxygen and you get very quick corrosion. 409 is ferritic, so it does rust, but the rust doesn't spall off the surface like carbon steel. The rust is therefore a protective layer.

304 is austenitic, so its protective corrosion layer is shiny silver, giving it the better appearance. As you noted, it will heat discolor.


As far as longevity, both will last basically forever in your application. 304 will look better except in the high heat areas where it will turn a little blue.

[Tom Vogel]

After all the work youve put in so far, Id go 304. If you havnt tig welded before, practice a bit on some scrap. Keep the heat down as far as possible and keep the torch moving. A colored bead is good, brown is not.

[Wasted Income]

304. Well worth the extra $100. It will look better for far longer, and 409 WILL eventually rust through. Been there, done that.

[Spartan]

If you really want to get tricky you can back purge the tube with Ar which will reduce the boogers of oxidized material inside. That's what I with ultra thin bicycle tubing...or you could build a cabinet to weld in (like a blast cabinet) which is what I built for titanium projects. The correct temperature and torch speed will give you a gold color bead. More heat equals darker colors like blue. Stainless welds like butter which I'm am guessing you know as well. If your budget allows the 304 is the way to go. As posted above 409 has iron in it and a magnet will stick, where 304 effectively has very little iron and more chrome and nickel (20% iirc) = no magnet sticking. As with any material not all 304 ss are created equal - there are grades. Exhaust gases are HYDROcarbons and 409 will rust more in places where water pools. My vote 304.
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[longbed67]

I agree purging when welding stainless is a must not only for oxides but to achieve better penetration and a consistent pit free weld. It is also easier to control the puddle with 304. I think the choice is clear the more points that are made and the more I really sit back and look at the facts! Thank you all for your input...