Abstract
Compared to other families of materials, metallic biomaterials are employed in medical devices for people more often. The efficacy and durability of an implant's material are influenced by its corrosion resistance, which also plays a major role in determining biocompatibility. The hostile environment inside the body presents several difficulties in preventing corrosion. Thus, a variety of methods have been employed to increase the corrosion resistance of biomaterials. Due to its higher corrosion rates given in this order (316L > CoCrMo > Ti-6Al-4V), 316L SS generally exhibits good corrosion resistance, albeit to a lesser extent than CoCr Mo and titanium alloys. They may, however, corrode in a very hostile environment brought on by the presence of chloride ions. Therefore, 316L SS implants need to have their corrosion resistance in simulated body fluids improved.
This work approaches the electrochemical behavior of the as received, heat-treated then water and furnace cooled 316L SS specimens immersed in simulated body fluids (0.9% NaCl). The specimen that presented the best corrosion resistance in the latter mentioned solution was eventually evaluated in Hanks Balanced Salt Solution enriched with Mg2+, Ca2+ ions (HBSS+). It was found that the corrosion resistance of heat-treated specimens cooled in the furnace deteriorated compared to the as-received specimen. This corrosion behavior could be explained by phase inhomogeneity mostly characterized by the presence of δ-Ferrite phases on which the cracks initiated. On the other hand, the water-quenched specimens characterized by the retained γ-austenite phase exhibits better corrosion resistance as compared to the as-received sample in 0.9% NaCl solution. However, the corrosion resistance of the specimen heat-treated at 1200 ⁰C, followed by water quenching (water 1200 ⁰C) deteriorated due to the galvanic effect in between the γ-Austenite and δ-Ferrite phases. Moreover, the specimen heat-treated at 1100 ⁰C followed by water quenching (water 1100 ⁰C) showed the best corrosion resistance for all specimens in 0.9% NaCl. This current improvement in corrosion resistance could be attributed to both effects of moderate uniform grain size and the full occurrence of the austenitic phase. On the contrary, the water 1100 ⁰C specimen showed poor corrosion resistance compared to as-received sample due to the aggressiveness of the HBSS+ solution.