Additively manufactured metals such as stainless steels have promising futures because of their adaptive and one-step fabrication. However, an understanding of their properties and behavior in corrosive environments has not yet been achieved. This is due to a lack of methodology used to study the morphology of interior surfaces in porous materials. Thus, this research investigates the corrosion characteristics of three-dimensional–printed stainless steels made with five volume printing powers. Accelerated corrosion experiments were conducted at 35°C–40°C under atmospheric pressure in salt fog under predesigned durations. Electrochemical study was carried out with a potentiostat. Tomographic studies were conducted using a scanning electron microscope and micro X-ray computed tomography technology to analyze the effects of corrosion. Results revealed three findings. First, corrosion took place internally for all additively manufactured stainless steel samples regardless of printing parameters. Second, localized corrosion between printed layers was most pronounced. Third, elongated and oriented internal pits formed during corrosion and were associated with a dendrite-like structure, which is different from the conventional understanding of subsurface pitting directed by gravity. This research not only generates new knowledge on additively manufactured stainless steels but also opens new revenues for future investigation on the design and additive manufacturing of metals and alloys.