Sigma Phase Detection in Duplex Stainless Steel Based on Correlation to Current and Potential in Micro Electrode Electrochemical of Surface

Abstract

Duplex stainless steels are widely used due to their good mechanical properties and corrosion resistance. However, they are susceptible to microstructural fragility related to harmful transformations taking place in intermetallic phases, such as the sigma phase. These transformations reduce mechanical properties like toughness and corrosion resistance. The current study aims to analyze the effect of different thermodynamic-and electrochemical-reactive phases based on using both linear sweep voltammetry tests as non-destructive tests, as well as the concept of microelectrodes. This technique is capable of detecting small amounts of intermetallic phases at the UNS-S31803 duplex stainless steel surface. Results have evidenced the influence of reduced electrode-solution exposure area on improving sensitivity for deleterious phase analyses. Peak potential and current peak recorded direct correlation to sigma phase concentration and it enabled detecting very low sigma-phase surface concentration, at the order of 0.04%. The study has shown improved sensitivity of linear sweep voltammetry tests used to detect harmful phases in duplex stainless steels.