Electrochemical behaviour of lotus-type porous SUS304L and SUS316L stainless steels

Lotus-type porous metals are expected to be used in various applications such as lightweight structural materials and biomedical materials. Lotus-type porous stainless steel is particularly promising as a structural material because stainless steel has useful properties such as high corrosion resistance, high workability, low cost and so on. However, there is a possibility that dissolved hydrogen or the microstructure of lotus-type porous stainless steel affects its corrosion behaviour. In this study, the electrochemical corrosion behaviour of lotus-type porous SUS304L and SUS316L stainless steels fabricated by the continuous zone melting technique under pressurized hydrogen was investigated using a potentiodynamic polarization in 0.1-kmol/m(3) sulphuric acid solution. The current density of lotus-type porous SUS304L was higher than that of nonporous SUS304L at around -100mV (-100mV peak), while it was similar to that of nonporous stainless steel in the passive and transpassive regions. The specific current peak observed for the porous SUS304L at around -100mV disappears when the pores are filled with epoxy resin or the specimens are dehydrogenated. Thus, it is concluded that the -100mV peak is attributed to the dissolved hydrogen at pore surface. In the case of lotus-type porous SUS316L, corrosion behaviour is similar to that of SUS304L.