Corrosion Mechanism Of Additively Manufactured 316 L Stainless Steel In 3.5 Wt.% Nacl Solution

Additively manufactured stainless steel has received widespread attention due to its excellent mechanical properties, while its corrosion mechanism in Cl?containing environments is still vague. This work investigates the pitting and passivation behavior of additively manufactured 316 L stainless steel (AM SS316 L) in 3.5 wt.% NaCl solution and its comparison to wrought counterpart, by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The results show that AM SS316 L exhibits a fine sub-grain structure with a diameter of approximately 5 mu m, and dislocations and Mo elements enriched at the sub-grain boundary. Compared with the wrought 316 L stainless steel (SS316 L), a large number of sub-grain boundaries and high dislocation density in AM SS316 L promote the formation of a more compact and thicker passive film, consequently enhances its general corrosion resistance. However, the low hydroxide content in the passive film and the micro-galvanic corrosion effect between Mo-rich sub-grain boundaries and sub-grains reduce the self-repairing ability of the passive film, thus the pitting corrosion resistance of AM SS316 L.