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 μm, 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.

增材制造的不锈钢因其出色的机械性能而受到广泛关注，而其在含氯环境中的腐蚀机理仍然模糊不清。这项工作通过扫描电子显微镜（SEM），X射线光电子能谱（XPS）研究了增材制造的316 L不锈钢（AM SS316 L）在3.5 wt％的NaCl溶液中的点蚀和钝化行为，并将其与锻造的对应物进行比较和电化学测量。结果表明，AM SS316 L表现出细小的亚晶粒结构，直径约为5μm，并且位错和Mo元素富集在亚晶粒边界。与锻造316 L不锈钢（SS316 L）相比，AM SS316 L中大量的亚晶界和高位错密度促进了更致密，更厚的钝化膜的形成，因此增强了其总体耐蚀性。但是，钝化膜中的低氢氧化物含量以及富Mo的亚晶界和亚晶粒之间的微电腐蚀作用降低了钝化膜的自修复能力，从而降低了AM SS316 L的耐点蚀性。