Influence of Cathodic Polarization on Passive Film and Corrosion Behavior of 2205 Duplex Stainless Steel in 0.9% wt. NaCl

Abstract

The influence of cathodic polarization on the electrochemical behavior of the passive film of stainless steels in physiological environments is significant. In such environments, hydrogen interactions and electrochemical modifications of this passive layer can directly affect the corrosion resistance and durability of these alloys. Although cathodic polarization has been widely studied regarding its effects on hydrogen embrittlement and stress corrosion cracking in 2205 Duplex Stainless Steel, the impact of such conditions on the electrical properties of the passive layer in physiological environments is inadequately researched. In this research the effects of cathodic polarization on the behavior of the passive film of 2205 duplex stainless steel in a 0.9% wt. NaCl solution were investigated. Electrochemical Impedance Spectroscopy and Mott-Schottky analysis were used to study passive film stability, semiconductor properties, and corrosion resistance. Results revealed that cathodic polarization introduced hydrogen into the passive film, decreasing the flat band potential to –0.08 V vs. Ag/AgCl, as well as increasing the donor density to 3.6x10²⁰ cm^-3. Electrochemical impedance spectroscopy suggested that the charge transfer resistance decreased, which is in good agreement with the passivity decay suggested by Mott-Schottky analysis. However, film thickness (1.9 nm) did not change, suggesting an electronic rather than structural changes in the passive film due to cathodic polarization. These findings highlighted the importance of understanding the trade-off between corrosion mitigation and hydrogen-induced film damage that might result from improper cathodic polarization practices.