Electrochemical engineering of passive films on AISI 304 stainless steel in H₂SO₄: The critical role of polarization slope in optimizing corrosion resistance

Authors

A. Márquez-Herrera, M. Zapata-Torres, S. Montesinos

Abstract

This study investigates an electrochemical strategy to enhance the corrosion resistance of AISI 304 stainless steel in 1 M H2SO4 through the active growth of a passive film. The performance of samples passivated using fixed potentiostatic potentials (CP) and potentiodynamic polarization (PD) was compared to untreated (control) samples and those treated according to the conventional ASTM A967 standard. Electrochemical Impedance Spectroscopy (EIS) data, fitted to an R(Q(RW)) circuit, revealed that samples polarized at potentials within the negative-slope region of the passive range developed a stable, highly protective film. This was evidenced by a dramatic increase in polarization resistance (e.g., 514 kΩ for CP03, compared to only 77 Ω for the control) and a corresponding drop in corrosion current density by several orders of magnitude (e.g., 0.0342 μA/cm2 vs. 303.1 μA/cm2). XPS analysis identified that the superior passive layer consists primarily of Cr2O3. Among all treatments, the potentiodynamic passivation (PD01) yielded the optimal performance (Icorr = 0.0183 μA/cm2, Rp = 1.26 MΩ). This work demonstrates that electrochemical passivation, particularly within the negative-slope region of the passive range, is a highly effective and rapid alternative to traditional chemical methods for achieving exceptional corrosion resistance in aggressive environments.

Keywords

AISI 304, Passivation, Corrosion, Tafel, EIS, XPS.