Life Prediction of Newly Developed Ferritic Stainless Steels for Automotive Muffler

Corrosion mechanism of automotive mufflers was investigated by SEM (scanning electron microscope) and XRD (X-ray diffractomer) analysis. 409L and newly developed 439M steels were evaluated in terms of condensate corrosion tests for 5 periods, 10 periods and 20 periods separately. The relative lifetimes of 409L and 439M steels were predicted according to the extreme value analysis method and pitting corrosion models. Modelling studies demonstrated that the predicted relative lifetime of 439M ferrite stainless steel is 6. 8 times that of 409L steels. The extreme value analysis method was also successfully used in the road test. The estimated maximum corrosion depth of the 439M muffler is 0. 55 mm.