The effect of oxide scale on the corrosion resistance of SUS301L stainless steel welding joints

The effect of thermal oxidates on the corrosion of SUS301L stainless steel welded joint was investigated using electrochemical corrosion test and TEM microstructure observation. Activation dissolution behavior without passive region was found in the potentiodynamic polarization curves on the welding zone and heat affected zone. The activation corrosion is related to the preferential dissolution of the Ni-Fe layer at the interface between chromium oxide and substrate. However, the passive region in the polarization curve reappears after the unstable Ni-Fe dissolves in the salt-frog test. The passivation behavior due to microstructure evolution beneath the thermal oxide film was discussed during the corrosion process.