Corrosion Behavior of Cold-Sprayed 316L Coatings: Effects of Deposition Temperature and Surface Condition

The passivation behavior of cold-sprayed 316L stainless steel coatings deposited onto SAE 1020 carbon steel was investigated with particular emphasis on the influence of surface condition and deposition temperature. Coatings produced at gas temperatures of 650-825 °C exhibited thicknesses of approximately 450-520 μm and porosity levels of about 5-7 vol.%, showing microstructures characterized by interparticle boundaries and incomplete bonding typical of cold-sprayed deposits. Electrochemical performance was evaluated in 0.6 M NaCl solution using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and cyclic potentiodynamic polarization (CPP). In the polished condition, the coatings consistently exhibited a shift toward more noble OCP values compared to both the as-sprayed state and the SAE 1020 substrate, indicating enhanced surface stability. Despite moderate polarization resistance and the presence of microstructural heterogeneities, EIS results revealed capacitive responses associated with passive-like surface films. Cyclic polarization further demonstrated that polished coatings are capable of sustaining anodic polarization without abrupt current increase, in contrast to the active behavior of the substrate, and in some cases showed evidence of repassivation. These findings indicate that surface finishing plays a critical role in stabilizing passive-like behavior, even in the presence of residual porosity. Overall, the results demonstrate that polished cold-sprayed 316L coatings effectively promote passivation and significantly improve the corrosion resistance of carbon steel substrates in chloride-containing environments.