Corrosion Behavior of Medium/Low Chromium Ferritic Stainless Steels in Condensate of Muffler

An oxidation-immersion-evaporation cyclic method was used to simulate the internal service environment of automotive muffler. The corrosion behavior of three medium/low chromium ferritic stainless steels (i.e., 409M, 425NT and 439M) was investigated comparatively in the condensate of automotive muffler to elucidate the effect of chromium content on their corrosion resistance. Experimental results revealed that the three stainless steels showed pitting corrosion after fifty cycles of tests and the main oxidation/corrosion products on steel surfaces were (Fe,Cr)₂O₃. With the increase of chromium content in the stainless steels, the specimens gradually showed higher corrosion potential and corrosion resistance, less pit number and depth values, and lower weight loss. These indicated that the increase of chromium content enhanced noticeably the corrosion resistance of ferritic stainless steel.