Comparative Study of the Influence of Aging Time at 850 °C on the Electrochemical Behaviour of Two Cast Super Duplex Stainless Steel

Two cast superduplex stainless steels were aged at 850°C for different times. The effect of aging on the electrochemical behaviour and hardness of both steels has been investigated. A comparative study between the two steels was carried out considering the difference in chemical composition between the alloys, that is, the presence of copper and tungsten in the 6A steel. Corrosion resistance was evaluated by potentiodynamic polarization test, electrochemical impedance spectroscopy and Mott Schottky analysis. The results showed the beneficial effect of 0.99%pCu and 0.70%pW addition to the cast SDSS retarding the embrittlement of the 6A steel aged at 850°C for 10 hours. The characteristic mechanism of localized corrosion in the aged samples for both materials was the selective dissolution of the ferrite phase.

Keywords:
Super duplex stainless steel; Sigma phase; Electrochemical behaviour; Copper