Grades Of Stainless
Is all stainless steel pretty much the same?
Although many people were working on a way to produce a corrosion resistant steel early in the 20th century and contributed to the accumulation of knowledge and technique that led to the result, Harry Brearley of the Brown-Firth research laboratory in Sheffield, England, is most commonly credited as the inventor of stainless steel. In 1913, while seeking an corrosion-resistant alloy for gun barrels, he discovered and subsequently industrialized a stainless steel alloy. In metallurgy, stainless steel is defined as a ferrous (iron) alloy with a minimum of 10.5 percent chromium content. The name originates from the fact that stainless steel doesn't stain, corrode, or rust as easily as ordinary steel.
In the aviation industry, this material is also called corrosion-resistant steel when its alloy type and grade isn't detailed. For most automotive OEMs, stainless steel became a necessity when the companies had to come to grips with the Federally mandated emissions-system warranties, since the exhaust system is part of the emissions system. These emissions system warranties required OEMs to develop a more durable exhaust tubing than the bare mild steel, which was notorious for rusting into oblivion within a few years, especially under salted-road winter conditions.
The answer was cost-effective 409 stainless steel, which is what is typically used on OEM applications. The 409 stainless has fair corrosion resistance and is magnetic due to the high ferrous metal content, but is a less expensive material than 304. The 409 is not an ideal material for a performance/restoration exhaust system, because it doesn't retain color, becoming brownish, and can rust and stain from exposure without ever being run.
OEMs build hundreds of thousands of cars, and few people who own them ever see the exhaust systems apart from the tips, therefore their appearance is not nearly as important as the millions saved with cheaper material. Also, stainless will outlast mild steel and will certainly get the car past the warranty period.
Conversely, 304 stainless steel has much better corrosion resistance and more nickel and non-ferrous (iron containing) metal content than 409. The 304 won't turn color from exposure and will only discolor slightly from getting very hot. It can be polished to a beautiful chrome-like finish and can be touched up with a chrome or aluminum polish. Although it will color somewhat with heat and time, not nearly as readily as the 409. Though we weren't able to get the materials grade on all the stainless systems for this story, the preceding explanation will help for those with the information available.
Although a few of the listed manufacturers sell direct to the consumer, we often found better deals from online dealers since the manufacturers must sell their units for full retail price. As you can probably guess, the Web sites varied dramatically in regard to available information, photos, and sound clips.
HPP also visited a number of online dealers to get an idea of street prices, but keep in mind that you will also have to pay shipping and tax in some cases. We hope you find this information useful if you decide to employ the second-most popular aftermarket upgrade to give your Pontiac more bark as well as bite!