You’ve got questions. We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we cover the differences between T-304 and T-409 stainless steel.

K.R. Fort Wayne, IN

Q: When shopping online, I notice a lot of stainless steel parts, such as exhaust components, are classified as “304 stainless steel” or “409 stainless steel.” Can you explain the difference? Which type is better for automotive use?

A: Generally, regular steel becomes stainless steel when chromium is added to it. Chromium is an element that produces a filmy texture, which serves as a barrier against corrosion, scratches, and cuts. The more chromium that is added to steel, the more stainless the steel becomes. This means that it becomes even more resistant to corrosion or oxidation. The addition of nickel content to the steel also enhances its resistance.

As you might imagine, the difference between T-304 and T-409 stainless steel lies in the chromium content. T-304 has more chromium than T-409–usually between 18 and 20 percent. It also has a nickel content between 8 and 10 percent. T-409 stainless steel, on the other hand, has a chromium content of 10.50 to 11.75 percent and its nickel content is only 0.50 percent.

If you are concerned about long-term appearance, then you should get the T-304 stainless steel products. Because of its higher chromium content, this type of stainless steel will not oxidize or rust and is considered more durable. However, if you’re more concerned about the price but want something that is fairly durable, then the T-409 will work just as well. Although it can show surface oxidation after a while, especially when exposed to calcium chloride or salt, a stainless steel cleanser can help prevent premature corrosion.