Corrosion Behavior of the AISI 316L Obtained by Selective Laser Melting in Simulated Inflammatory Conditions

The biological response of the AISI 316L austenitic stainless steel orthopedic implants, obtained by additive manufacturing, exposed to simulated inflammatory states was studied in this work. Corrosion tests of selected laser melted parts was performed for TiN coated and no-coated surfaces in normal human biological state and simulated inflammatory conditions. Tests were conducted in synthetic physiological Ringer’s solution at 37 ℃. To simulate inflammatory state samples were immersed in a combination of Ringer’s solution and 150 mM of hydrogen peroxide (H2O2) for 48 h. Results shows that, for simulated inflammatory state, surface roughness was increased from 6 to 9 µm and corrosion resistance of selective laser melted surfaces was decreased as a consequence of the interaction with the H2O2 rich solution. For TiN coated surfaces results reveals a more electropositive corrosion potential Ecorr. Nevertheless, pitting potential Epitt drop significantly. In fact, the highly oxidizing proprieties of hydrogen peroxide promotes aggressive and localized corrosion which increase the instability of passivation and in consequence strongly alter the corrosion properties.