An Electrochemical Study of the Corrosion Behaviour of the Polished Atomic Diffusion Additive Manufactured 17-4PH Stainless Steel Using Centrifugal Mass Finishing Method in Saltwater.

Additive manufacturing (AM) enables the fabrication of complex geometries and high-performance alloys such as 17-4PH stainless steel. However, the surface defects inherent to AM components compromise corrosion resistance. The post surface treatment can reduce and eliminate these defects. This study examines the effect of centrifugal mass finishing on the corrosion behaviour of 17-4PH stainless steel produced by AM. Corrosion behaviour of the samples in a 0.6 M NaCl solution is assessed using electrochemical technique testing, including asymmetry electrochemical nose, potentiodynamic polarisation curves, electrochemical impedance spectroscopy, and Mott-Schottky. All electrochemical testing were conducted in concordance with the specifications of ASTM standards. The electrochemical impedance spectroscopy were performed over period ranging from 2 h to 96 h with intervals of approximately one day. Finished specimens exhibit significantly improved corrosion resistance compared with as-built counterparts. Notably, the polished surfaces demonstrate spontaneous oxidised layer recovery between -0.297 V and 0 V, indicative of the enhancement of the protection during early immersion stages. This behaviour is attributed to surface modifications induced by the finishing process, including reduced roughness in 78% and imperfections. These findings highlight the importance of optimising post-processing protocols to improve the durability of AM stainless steels in aggressive environments.