Corrosion of SLM 316L Stainless Steel in Simulated Body Fluid

Additive manufacturing methods, such as selective laser melting (SLM) can enable more intricate metal parts to be fabricated, while minimizing wasted materials and lowering manufacturing costs. Using SLM to fabricate stainless steel parts tailored for surgical implants can enable more customized parts with potentially greater biocompatibility, corrosion resistance, and longevity. In particular, many internal fixation devices (e.g., wires, pins, screws, and intramedullary nails or rods) are stainless steel, specifically 316L; thereby, providing a high elastic modulus and rigidity.1,2 The presence of chloride ions and reduced sulfur compounds in body fluids can initiate pitting and crevice corrosion involving the loosening of screws, thus endangering the secure fit of the plates or implant structures. Both types of corrosion have occurred in implants where inclusions, cracks, or other surface defects were present. The fabrication methods used to form 316L surgical parts influence the microstructure, which subsequently impacts the corrosion behavior. Although there are numerous corrosion studies on 316L parts fabricated by SLM, the results are not conclusive. Variation in processing parameters, along with partially described processing conditions make it challenging to fully interpret which fabrication conditions will yield a SLM 316L part with optimal corrosion properties. Thus, studies that continue to explore the relationship between SLM processing procedures and resulting microstructural properties of 316L parts that are correlated with corrosion behavior are necessary for the advancement of additive manufacturing of surgical grade stainless steel.