The effects of heat treatment and surface state on the corrosion resistance of laser powder bed fusion 304L stainless steel in 3.5 wt% NaCl solution

The corrosion resistance of laser powder bed fusion (LPBF) 304L stainless steel (SS) in 3.5 wt% NaCl solution was evaluated at room temperature through potentiodynamic polarization and electrochemical impedance spectroscopy tests. For electropolished samples, annealing at 1200 degrees C slightly enhanced the corrosion resistance due to changes in crystal orientation and inclusion composition, and reduced residual strain. In contrast, annealing at 1050 degrees C significantly reduced the corrosion resistance mainly due to the disappearance of dislocation cells and the remained residual dislocations. Residual stress/strain and martensitic transformation induced by sandpaper grinding can also deteriorate the corrosion resistance. Only the as-received sample shows stable passivation regardless of the surface conditions.