Embrittlement of a Duplex Stainless Steel in Acidic Environment Under Applied Cathodic Potentials

Abstract

Hydrogen-induced degradation of mechanical properties of a duplex stainless steel in 0.1N H 2 SO 4 solution has been studied under in situ cathodic charging conditions. Significant reductions in percentage of elongation, toughness, and time to failure were noticed due to the ingress of hydrogen into the material at various applied cathodic potentials in the range of -200 to -800 mV (SCE). Cleavage fractures were identified mainly in the ferritic phases. Crack growth was observed to be inhibited by the austenite phase. However, depending on the severity of the environment, both the ferrite and austenite phases could be embrittled. At less negative potentials, presence of surface film and low hydrogen fugacity seemed to control hydrogen ingress in the metal. Addition of thiosulfate to the acidic solution further degraded the mechanical properties of the steel at the applied cathodic potential.

Stress Corrosion Cracking of Duplex Stainless Steels

“…Even under HE conditions, a selective dissolution of ferrite was reported by the authors. Roychowdhury and Kain [25] observed a progressive deterioration in ductility with higher cathodic overpotentials for a 2205 DSS. The fracture was through transgranular cleavage mostly in the ferrite, the austenite ligaments separating by ductile tearing.…”

“…• super-duplex and hyper-duplex steels, with [25][26] Cr and increased Mo and N compared with the 25 Cr grades, including grades such as 2507, Zeron100, SAF 2707 HD.…”

On the Role of HISC on Super and Hyper Duplex Stainless Steel Tubes

“…Due to the excellent agreement of properties, these steels grade are widely employed in the petroleum industry, highlighting in offshore applications as subsea equipments, umbilical tubes and liner pipes [5,16,18,21]. The synergic effect between both phases promotes a good combination of high mechanical strength and excellent resistance to stress corrosion cracking in chloride solutions, as well as in the presence of H 2 S and CO 2 .…”