Influence of deformation induced martensitic (alpha') phase transformation and compressive residual stresses on electrochemical properties of austenitic (gamma) 321 steel laser peened without protective coating in acidic solution was investigated. Peening induced compressive residual stresses lowered the corrosion rate 19 times compared to untreated condition, subdued the deleterious role of alpha' phase. Presence of dual phases (gamma and alpha') ensued multiple peaks in the active region of the polarization curve and pitting at ce phase sites. Roughness after peening (<= 1 mu m) had no effect on corrosion properties. A fivefold increase in charge transfer resistance observed after peening. (C) 2017 Elsevier B.V. All rights reserved.