Effect of Grain Size on the Anodic Dissolution of Lean Duplex UNS S32202 Austenitic-Ferritic Stainless Steel

The effect of grain size on the anodic dissolution of lean duplex UNS S32202 dual-phase austenitic-ferritic stainless steel was evaluated. Grain coarsening was achieved by heat treatment, and grain size and grain boundary densities determined by automatic image analysis after etching. Potentiodynamic electrochemical testing in acidic chloride medium allowed isolating the anodic dissolution behavior of the crystallographic phases of the material. A relationship between grain boundary density (for grain sizes in the micrometer range) and dissolution rate has been found, showing that reducing grain size enhances active corrosion rates in environments that promote active behavior. This leads to new possibilities of industrial adjustment of the corrosion behavior of duplex stainless steels via grain size control.