A study of the selective dissolution behavior of duplex stainless steel by micro-electrochemical technique

Abstract

The Ag-AgCl micro-reference electrodes were fabricated and used to determine the potentials of ferrite and austenite in duplex stainless steel in NaCl solutions separately. The result shows that ferrite has lower corrosion potential than that of austenite. To determine the corrosion behavior for the single phases accurately and obtain more information about the selective corrosion, a capillary-based micro electrochemical system was established. The electrochemical determinations of ferrite and austenite were performed respectively in solutions containing nitric acid and FeCl3. According to the results, ferrite has more noble corrosion potential and low current density in 1.5 mol/L HNO3 and 1.5 mol/L HNO3 + 0.5 mol/L FeCl3 solutions, thus selective corrosion occurred in austenite phase, while, in 1.5 mol/L HNO3+0.1 mol/L FeCl3 solutions, the potential differences between two phases are not obvious, which result in little selective corrosion.