Localized corrosion resistance of 409 L and 430 ferritic stainless steels

The pitting corrosion and intergranular corrosion resistance performances of 409 L and 430 hot-rolling plates were contrastively investigated by using electrochemical measurements and chemical immersion tests.The results show that the difference between breakdown potential and protection potential of 409 L stainless steel is little,and the restorability of the passive film is strong with small-scale shallow pits.The pitting corrosion resistance of 430 stainless steel is better than that of 409 L stainless steel because of a higher breakdown potential,but its banding microstructure has the apparent effect of a corrosion microcell,represented with a more serious general corrosion.The intergranular corrosion resistance of 409 L stainless steel performs worse than that of the 430 stainless steel because of the low content of Cr and the lack of stabilizing processes under the hot-rolled condition.Through microstructure analysis,409 L stainless steel presents a classic intergranular corrosion appearance along equiaxial grain boundaries,while 430 stainless steel exhibits a delamination corrosion trace at the phase interface between carbides(M₂₃C₆) and the matrix.