A survey on the passivity of tempered AISI 420 martensitic stainless steel

Highlights: • Tempering adversely influences corrosion performance of martensitic stainless steel. • Passive films formed on tempered samples do not show p-type semiconducting behavior. • Anodization in sulfuric acid bath leads to formation of less intact passive films. • By increasing anodizing time, more defective passive films are formed. • Tempering considerably increases point defect densities of resulting passive layers. This research aims to investigate the impact of tempering and passivation times on the electrochemical and structural properties of passive films forming on the surface of martensitic stainless steel using double-loop electrochemical potentiodynamic reactivation, anodic potentiodynamic polarization, Mott-Schottky, Vickers microhardness and X-ray diffraction techniques. The results indicated that less internally-stressed samples possess denser and less defective passive films on their surfaces, which can be attributed to the presence of higher concentration of metal ions at the metal/solution interface during anodization process. Moreover, prolonged passivation times led to incorporation of more impurities into the growing passive film, deteriorating its electrochemical properties.