Pitting Behaviour of Lean Duplex Stainless Steels in Marine and Oilfield Environments

Abstract

Abstract Lean Duplex stainless steels are becoming attractive for applications in oilfield and marine environments due to their economic advantages, very good mechanical properties and relatively good corrosion resistance. However, there is little information about the pitting behaviour of lean Duplex stainless steels in oilfield and marine environments. This paper discusses the tendency for pitting corrosion to initiate through an evaluation of breakdown potentials of lean Duplex stainless steels UNS S32101, UNS S32304, LDX2404, standard Duplex stainless steel UNS S32205 and Austenitic stainless steels, 304L and 316L in aerated 3.5% NaCl and a CO2-saturated oilfield brine solution. Electrochemical measurements were made using a three-electrode electrochemical set up using an Ag/AgCl reference electrode and a platinum counter electrode. The results showed that breakdown potentials are generally higher in aerated 3.5% NaCl than the CO2-saturated oilfield brine solution for all the alloys tested. Lean Duplex stainless steel UNS S32101 and Austenitic stainless steel 304L showed comparable breakdown potentials in both environments while lean Duplex stainless steel UNS S32304 and Austenitic stainless steel 316L also have comparable breakdown potentials. There does not seem to be a universal relationship between Pitting Resistant Equivalent number and breakdown potential for the lean Duplex and Austenitic stainless steels.