Pitting corrosion behaviour of austenitic stainless steels with Cu and Sn additions

The influence of Cu and Sn on the pitting corrosion resistance of AISI 304 and 316 stainless steels in chloride-containing media has been investigated. The corrosion behaviour was evaluated by cyclic polarization, potentiostatic CPT measurements and electrochemical impedance spectroscopy in 3.5 wt% NaCl. The corrosion resistance was also studied in FeCl₃ under Standard ASTM G-48. According to the results, Cu addition favours pit nucleation but inhibits its growth, whereas Sn exerts the opposite effect, favouring pit growth and inhibiting its nucleation. Studies by SEM, X-ray mapping and EDS analysis showed Cu-, Cl- and O-rich corrosion products that reduce the extent of corrosion damage.