Application of the Modified Electrochemical Potentiokinetic Reactivation Test to Study Passivity and Corrosion of Metals in Aqueous Solutions

To apply the electrochemical potentiokinetic reactivation (EPR) test to study corrosion phenomena other than sensitization and intergranular corrosion in Fe-Cr-Ni alloys, the mechanism of the EPR test is discussed, and examples of its broad applicability are given. More complete insight into the active-passive transition process is provided by the EPR test compared to traditional anodic polarization measurements. A modified EPR test was used to study passivity and corrosion of 1018 steel, chromium, nickel, and AISI 321 (UNS S32100) stainless steels in sulfuric acid (H₂SO₄) and nitric acid (HNO₃) solutions. The test results show that electrochemical information measured in the breakdown of anodic passivity of a metal-aqueous solution system is important in understanding the nature of passivity and corrosion. The test results show that the anodic reactivation is a common phenomenon, and chemical activators like potassium thiocyanate (KSCN) are often not required; thus, a modified EPR test can provide important insights into passivity and corrosion of many metal/environment systems.