Corrosion behavior of a new developed ferritic stainless steels used in automobile exhaust system

摘要

The inside corrosion of failed automotive mufflers collected in China was investigated and the composition of the automotive exhaust gas condensate collected from HONGQI automobile was analyzed. According to the analyzed result of collected condensate's composition, the corrosion resistance of a new designed high Cr stainless steel (B439M) bearing Nb and Ti and a low Cr T409L stainless steel were studied with a condensate corrosion test method which simulates the inside corrosion of automotive mufflers. The life of the two materials was estimated by extreme value analysis of the maximum corrosion depth obtained by the dip dry test (DDT). The life of type B439M steel was 1.6 times as long as that of type T409L steel. To clarify the corrosive process of the simulated condensate test, the electron work function (EWF) on the two stainless steels' surface was evaluated. It was demonstrated that the surface of new designed stainless steel exhibited markedly improved resistances to corrosion during a simulated condensate test cycle and the corrosive process of simulated condensate test was evaluated and discussed.