## 1 Introduction
The safety of hydrogen storage systems depends on selecting suitable materials for critical components, including fittings, valves, connectors, container walls, and pipelines [3]. Type I pressure vessels, as well as the metallic components of other types, such as liners and bosses, are commonly made from stainless steel, high Cr-Ni-Mo alloyed steels, or aluminum alloys [6,13,15]. Unlike body-centered cubic (BCC) structures, face-centered cubic (FCC) materials exhibit minimal hydrogen diffusion due to their low diffusion coefficient at ambient and low temperatures [13,16]. Austenitic stainless steel is widely used for hydrogen storage and transportation due to its high resistance to hydrogen embrittlement, attributed to low hydrogen diffusivity and high solubility at room temperature [7,9,16]. The chemical composition, manufacturing method, and heat treatment of stainless steel alloys significantly influence both their mechanical properties and hydrogen embrittlement behavior [16,17,18,19]. Type I pressure vessels, as well as the liners for Type II and III vessels, are typically manufactured using a combination of rolling, welding, casting, heat treatment, and drilling [7; 15; 17]. While these methods are well-established and cost-effective, they impose geometric limitations [7; 15; 17]. In industrial applications, Type I pressure vessels made of 316L stainless steel are commonly used for hydrogen storage at pressures ranging from 20 to 30 MPa [6]. Additive manufacturing (AM) enables the fabrication of intricate 3D geometries, allowing for the production of highly functional components with reduced lead time and lower costs. This efficiency has increased interest in AM for manufacturing specialized metallic parts designed to withstand harsh operating conditions, such as those encountered in hydrogen technology [7; 17; 18; 19; 20]. Laser powder bed fusion (LPBF) is one of the most widely used AM techniques for metal fabrication [7; 9; 17; 18; 20; 21]. The LPBF process is characterized by high cooling rates during solidification and complex thermal gradients [18]. As a result, additively manufactured 316L stainless steel typically exhibits higher strength due to the fine microstructure formed during processing [16]. [PERSON] et al. [17] used AM to fabricate a 316L stainless steel pressure vessel and reported failure between 67 and 70 MPa. Similarly, [PERSON] et al. [21] highlighted the widespread use of AM 316L stainless steel in cryogenic applications, citing its excellent corrosion resistance and extremely low ductile-to-brittle transition temperature. The hydrogen embrittlement (HE) sensitivity of additively manufactured (AM) 316L stainless steel is expected to differ from that of conventionally manufactured 316L. Understanding the fabrication process and structural characteristics of hydrogen storage materials is essential for comprehending the HE mechanisms in storage tanks [3]. Current research on the HE behavior of AM 316L stainless steel has primarily focused on microstructural analysis and embrittlement mechanisms across various AM metals. However, studies remain limited, particularly in evaluating the impact of post-processing heat treatments (PPHT) on the hydrogen embrittlement resistance of AM materials. This gap highlights the need for further investigation into the correlation between AM processing conditions, heat treatment, and HE performance. [PERSON] et al. [22] investigated the hydrogen embrittlement (HE) behavior of additively manufactured (AM) 316L stainless steel, reporting lower ductility and greater HE susceptibility compared to thermomechanically processed 316L stainless steel. They attributed this increased HE susceptibility to factors such as high residual stress, greater porosity, and faster hydrogen diffusion in AM 316L stainless steel. Similarly, [PERSON] et al. [23] found that the HE susceptibility of AM 316L stainless steel is strongly influenced by its initial microstructure, particularly the morphology and density of dislocations.