The influence of Cu on the pitting corrosion of duplex stainless steel UNS S32550

Electrochemical studies and metallurgical methods were used to study the influence of Cu on the microstructure and corrosion behavior of 25% Cr Duplex Stainless Steels in chloride-containing neutral and acid solutions. Similar alloys with different Cu content were used to determine the effect of Cu on their corrosion resistance. Copper which has been found to enhance the resistance of these steels in sulfuric acid has been shown to be useful in improving their pitting resistance in both 1 M HCl and 3.5% NaCl. In HCl the variation in the current density in the active state showed a substantial reduction of the peak for the Cu-containing alloys. Also, the CPT (Critical Pitting Temperature) was slightly improved by the addition of Cu. Measurements of the pitting potential in both HCl and NaCl showed that Cu in alloys of type UNS S32550 has a significant positive effect on their corrosion resistance in chloride containing solutions. Pitting in both environments took place preferentially in the ferrite phase. The addition of Cu and its influence on the number of initiation events is discussed