This work investigates the corrosion resistance of activated-TIG (A-TIG) welded AISI 304L stainless steel using TiO₂, CuO, and CaCO₃ 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 5 mm plates, and corrosion behavior was examined in 3.5 wt.% NaCl using open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The OCP values stabilized in a moderately passive window, with CaCO₃ showing the noblest potential (-0.1946 V), TiO₂ slightly lower (-0.2258 V), and CuO the most negative (-0.2870 V). In contrast, EIS revealed clear flux-dependent differences in kinetic resistance: TiO₂-treated welds exhibited the highest polarization resistance and low-frequency impedance (10⁵–10⁶ Ω), CuO welds showed intermediate resistance, while CaCO₃ welds displayed the lowest resistance. Nyquist plots showed depressed semicircles with diameters proportional to Rp, while Bode plots confirmed consistent solution resistance (~18–20 Ω) and significant divergence at low frequencies. Phase spectra indicated single dominant time constants, with TiO₂ producing the most stable and compact passive film, CuO showing moderate stability, and CaCO₃ resulting in a less protective and porous layer. Overall, TiO₂ 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.

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