Invesigation of the corrosion behavior of 316l steel produced by directed energy deposition method

In this study, the corrosion behavior of AISI 316L stainless steel produced by Direct Energy Deposition (DED) in a 0.5 M NaCl solution was investigated in comparison with conventionally manufactured 316L. The experimental program employed open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PD) tests; microstructural changes before and after corrosion were evaluated using optical microscopy and SEM–EDS. OCP measurements shifted positively over time for all specimens, confirming passive film formation. EIS analyses showed that the DED 316L F1 specimen exhibited the highest passive-film stability with Rp = 8.07×10^5 Ω·cm^2 and CR = 0.015 mpy, while conventional specimens yielded Rp values in the ~2.29×10^4–4.88×10^4 Ω·cm^2 range. An α parameter of 0.93–0.95 indicates a highly capacitive and continuous passive layer. The overall corrosion-resistance ranking is: DED 316L F1 > DED 316L F4 > DED 316L F3 > DED 316L F2 > Conventional 316L F3 > Conventional 316L F1 > Conventional 316L F2. In PD tests for conventional 316L, for example, F1 yielded Ecorr = −177 mV and Icorr = 667 nA, whereas F2 showed Ecorr = −150 mV and Icorr = 1.25 μA; F3 exhibited the lowest corrosion rate. By contrast, DED 316L specimens tended to display more negative Ecorr and higher Icorr. These findings demonstrate that DED processing parameters critically determine corrosion behavior and that, with appropriate settings, DED 316L can achieve passive-film stability and low corrosion rates surpassing those of conventional 316L; nevertheless, control of microstructural heterogeneity and porosity remains essential.