Electrochemical Impedance Spectroscopy Assessment of Corrosion Resistance in A-TIG Welded AISI ۳۰۴L Stainless Steel Using Different Activating Fluxes

This work investigates the corrosion resistance of activated-TIG (A-TIG) welded AISI ۳۰۴L stainless steel using TiO۲, CuO, and CaCO۳ fluxes. Corrosion performance of weld cross-sections is a key concern for stainless steels in marine, chemical, and food-processing industries, where chloride-induced degradation limits service life. Bead-on-plate welds were produced on ۵ mm plates, and corrosion behavior was examined in ۳.۵ wt.% NaCl using open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The OCP values stabilized in a moderately passive window, with CaCO۳ showing the noblest potential (-۰.۱۹۴۶ V), TiO۲ slightly lower (-۰.۲۲۵۸ V), and CuO the most negative (-۰.۲۸۷۰ V). In contrast, EIS revealed clear flux-dependent differences in kinetic resistance: TiO۲-treated welds exhibited the highest polarization resistance and low-frequency impedance (۱۰۵-۱۰۶ Ω), CuO welds showed intermediate resistance, while CaCO۳ welds displayed the lowest resistance. Nyquist plots showed depressed semicircles with diameters proportional to Rp, while Bode plots confirmed consistent solution resistance (~۱۸-۲۰ Ω) and significant divergence at low frequencies. Phase spectra indicated single dominant time constants, with TiO۲ producing the most stable and compact passive film, CuO showing moderate stability, and CaCO۳ resulting in a less protective and porous layer. Overall, TiO۲ was the most effective flux for enhancing passive-film integrity, underlining the critical role of flux chemistry in corrosion resistance of A-TIG welded stainless steels.

کلیدواژه ها:

AISI ۳۰۴L stainless steel ، TIG welding ، Activated TIG (A-TIG) ، Electrochemical Impedance Spectroscopy (EIS) ، Corrosion resistance ، Passive film stability