In-situ Anodic Polarization with Concurrent Imaging of Precursor Sites for Pitting in UNS S32305 Duplex Stainless Steels in Chloride and Sour Environments

摘要

A new methodology to study in-situ the pitting corrosion of stainless steels at high temperature and high pressure (HT/HP) was developed. This methodology allowed the real-time in-situ anodic polarization while determining the sites for pit initiation in UNS S32305 (22% Cr Duplex Stainless Steels), in chloride containing environments with additions of H_2S and CO_2 at high temperature and pressure. The methodology allowed measurements at two temperatures 40°C (and 582 psi) and 180°C (and 752 psi). This methodology allowed the in-situ imaging of metastable pitting as well as stable pitting under different conditions. Pitting corrosion developed in inclusions (5-10 micrometer or larger); which are mainly composed of intermetallic particles containing significant amounts of B, N, O, Mg, Al, S, Ca and C.