Automobile exhaust pipes come in all sizes and shapes, but most are made of either aluminized steel or stainless steel. Both have their advantages; which one you choose largely comes down to a matter of need and budget.
Aluminized steel is standard steel tubing with a thin coating of aluminum on the inside and outside. The aluminum forms an oxide layer to keep the steel beneath from corroding. Stainless steel pipes are made of pure steel containing a certain percentage of nickel and chrome, which keeps the material from corroding under any conditions.
This material is far cheaper and a bit lighter than stainless steel, making it the default choice for most exhaust systems. However, even a tiny scratch in the aluminum oxide finish can allow the metal beneath to rust, and the cut pipe ends remain exposed to air and moisture.
Stainless steel is corrosion resistant all the way through, so no scratch or cut can cause it to rust. Car enthusiasts also prefer stainless steel for its ability to take a polish and hold its chrome-like shine for years.
