What You Should Know About Stainless Steel

What You Should Know About Stainless Steel

Not all stainless steel exhaust systems are the same – and that’s a good thing 

When it comes to stainless steel materials, not all exhaust systems are equal. Most current aftermarket exhaust systems are made of two alloys – 409SS and 304SS. In a purely simplistic manner, most exhaust tips are made from 304 and highly polished to give that attractive shiny “bling.” A 409 stainless steel is more dull steel and used for mufflers and exhaust tubing. Both materials are great for exhaust systems but they have very different properties.

A 304 stainless steel contains more chromium than 409 and thus can be polished to a high shine – not unlike a chrome bumper. It is harder and more brittle than the 409, which is softer and more malleable. For this reason we use the 304 only for tips and 409 for all other exhaust parts including the muffler. This avoids cracking at critical points such as muffler inlet/outlet points, hard tubing bends, muffler edges and tubing seams. 

It is important to note, in all fairness, that 409 stainless steel will pick up a brown surface coloration over a period of time on the vehicle. This is due to a normal process of condensation and environmental elements such as rain and snow generating a light surface rust. This matter will NOT affect the exhaust sound or the classic rust through that occurred in the past with old style aluminized steel that would break down quickly. And due to the fact that the 409SS section of our exhaust is under the car and not visible once installed, we have decided that system durability should be the decision maker on material selection.

At Legato, we use 409SS materials for all of our exhaust with the exception of the 304SS tips. This combination delivers the most durable exhaust possible – a crack resistant muffler and tubing system that will flex with vibration and heat expansion but not crack. We top it off with a beautiful 304SS exhaust tip that is elegant and tasteful.


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