Corrosion of Materials for Automotive Exhaust Systems

A survey was performed on 100 late-model automotive exhaust systems that had been replaced because of corrosion, to determine the materials of construction and locations of failure. Concurrently, laboratory tests were performed on exhaust materials to determine their ranking in both salt and synthetic exhaust condensate.

Aluminized carbon steel systems were found to have a probable life expectancy of less than five years, while bare Type 409 stainless steel was projected to last somewhat more than five years. Bare Type 409 stainless was severely attacked in laboratory tests, followed by bare Type 439, Type 430M, and aluminized Type 409 stainless, in increasing order of corrosion resistance.