The effect of copper and molybdenum on pitting corrosion and stress corrosion cracking behavior of ultra-pure ferritic stainless steels

The work addresses the influence of Cu and Mo additions on corrosion resistance of ferritic stainless steels in chloride media. According to the results, 0.5% Cu addition and the precipitation of ε-Cu phases decreased the pitting corrosion resistance in chloride media. The addition of both Cu and Mo to 19% Cr ferritic stainless steels causes SCC and the susceptibility to SCC increases with the aging treatment. The SCC initiated from pitting of ε-Cu phases and was mostly intergranular. The selective dissolution and repassivation of Mo promoted the second corrosion grooves parallel to stress.

► 0.5% Cu addition reduces pitting corrosion resistance in investigated steels.
► Aging promotes precipitation of ε-Cu phases and decreases the corrosion resistance.
► Cu and Mo elements simultaneously added in tested steels causes the SCC.
► The susceptibility to SCC increases with the aging treatment.
► SCC initiates from pitting of ε-Cu and propagates to Mo atoms parallel to stress.