Corrosion behavior of additively manufactured 316L stainless steel in acidic media

Recently, additive manufacturing has got tremendous attention due to ease in the production of complex metallic parts for different applications i.e. aerospace, petrochemical etc. However, there is a scarcity of literature, addressing the corrosion behavior of additive manufactured (AM) alloys. This study presents, the chemical composition and corrosion response of the passive oxide film formed on the AM 316L stainless steel in acidic regime (pH <= 3) and its comparison to wrought counterpart, by applying X-ray photoelectron spectroscopy (XPS) and electrochemical analysis, respectively. Microstructural characterization of AM specimen revealed the presence of nanometer-ranged ripples type sub-granular structure confined within the macro grains. XPS analysis indicated the formation of mono layered and bi layered passive oxide film in pH 1 and 3 electrolytes, respectively. Interestingly, higher charge transfer resistance (50 times) and significantly decreased corrosion current density (2 order of magnitude) in aggressively acidic solution (pH 1) has been observed by AM specimens compared to conventional wrought 316L stainless steel. The higher corrosion resistance has been attributed to the development of fine sub-granular structure, which most likely regulates the stability of the passive oxide film and the raid solidification rate (approx. 107 K/s) involved in the additive manufacturing process rationalizing the reduction of MnS inclusions. In comparison, a significantly higher corrosion resistance by the AM 316L stainless steel in highly acidic environment (pH <= 3) has been recoded, surpassing the conventional wrought material.