Influence of Centerline Intermetallic Stringers on Pitting Corrosion Resistance of Superduplex Stainless Steel

Abstract Superduplex stainless steel UNS S32750 / EN 1.4410 is commonly used in marine environment, petrochemical, oil and gas, chemical and desalination industries, requiring materials with superior corrosion and mechanical properties. Very few residual intermetallic particles may be present under the form of centerline stringers whose effects on corrosion properties are not well documented. A previous study demonstrated the negligible influence of the intermetallic phases in centerline stringers (typically < 0.1% over thickness) on the hydrogen embrittlement susceptibility of superduplex stainless steel [1]. The present study aims at highlighting the impact of centerline intermetallic stringers on pitting corrosion resistance. Samples containing σ-phase only within segregated centerline area have been intentionally produced in the laboratory. After detailed microstructural characterization, ASTM G48 Method A tests and long term immersion tests have been conducted to demonstrate that very few intermetallic phases within segregated bands don’t lead to a loss of pitting resistance. Then macroscopic and microscopic electrochemical investigations were performed on samples with centerline intermetallic stringers to highlight the weak points of microstructure regarding corrosion properties.