Additive manufacturing (AM) is a rapidly growing metal processing technique that not only enables the making of complex geometries that are difficult to produce by using traditional methods. Stainless steel 316L displays high resistance to localized corrosion attack by chloride due to the presence of molybdenum and chromium leading to the formation of a stable passive film. In this work, we aim to characterize and compare the active-passive characteristics of stainless steel 316L manufactured using directed energy deposition (DED) and selective laser melting (SLM) techniques. The effect of anisotropy was also studied by obtaining samples perpendicular and parallel to the building direction. The testing solution used was 3.5 wt% NaCl maintained at a pH of 8 adjusted by borate buffer. A comprehensive understanding of corrosion performance of materials was obtained by testing using cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS). The tested alloys were characterized to understand the mechanism of chloride attack on the microstructural features of the AM alloy.

Additive manufacturing (AM) techniques are being studied widely for producing intricately shaped parts and structural components with superior mechanical properties and corrosion resistance. Several detailed studies [1-9] have been performed on selective laser melted (SLM) stainless steel 316L (SS316L) alloys which describe the effects of process parameters, anisotropy and heat treatments on the corrosion behavior of these alloys. These studies have revealed various pit morphologies and passive films formed on the alloys in various solutions. Among other commonly studied additive manufacturing techniques, directed energy deposition (DED) has also been gaining attention due to its ability to be used to build large parts, repair existing parts and produce parts with high density [10,11]. There have been few studies on the corrosion behavior of SS316L alloys manufactured using DED [12,13] but no detailed studies have been performed on the pit morphologies or effect of anisotropy on the corrosion resistance of these alloys.